The movie opens with Dr. John Watson (Jude Law) and Inspector Lestrade (Eddie Marsan) riding in a carriage in the middle of the night. The scene cuts from the carriage to Sherlock Holmes (Robert Downey Jr.) who is following on foot. He's in a tremendous hurry - he darts between columns, up and down stairs and around buildings effortlessly - and finally enters a non-descript building.

Once inside, Holmes starts running down a spiral staircase, but pauses when he notices a ruffian who is standing guard. He analyzes the situation (the audience actually sees in slow-motion how Holmes plans to take the ruffian guard out), and then disarms the ruffian. Holmes continues running down the stairs, until he reaches the basement, where a black magic ritual is taking place. Holmes hides behind a column to assess the situation again.

In the center of the room, there's a girl wearing a white dress and lying on a table, while a hooded figure stands over her chanting. Scattered across the room are several other hooded figures and ruffian guards. Holmes begins calculating how to take them out, but is interrupted when a guard comes up from behind him. He fights with the guard, then Watson shows up and helps Holmes choke the man. They greet each other with amusing banter (their friendship is very much written as a bromance, and come up at several points in the film), where Watson chides Holmes for forgetting to bring his pistol AND forgetting to turn off the stove.

Once the fighting really begins, most of the other hooded figures scatter. The main figure standing over the girl stays however, and his chanting begins to reach a feverish pitch. Holmes continues to fight and is helped by Watson.

Back at the table, the (possibly possessed) girl reaches up for a dagger and makes to stab herself. Holmes hurries over and stops her just in time. The hooded figure stops to greet Sherlock by name, and is revealed to be Lord Blackwood (Mark Strong). As he taunts Sherlock, Watson comes running over, but is stopped by Holmes. Turns out, Lord Blackwood had some kind of glass knife that would have pierced Watson if he had gotten any closer. Holmes directs Watson to put his energies into tending the girl, and Lestrade and his men burst in just in the nick of time.

As Blackwood is led off by Scotland Yard, Lestrade chides Holmes for not waiting for Lestrade's orders. Holmes says that the girls parents hired him, so he doesn't report to Lestrade. Before Lestrade can retort, a newspaper photographer who wants to take their picture interrupts him. Holmes throws up an arm and prevents the camera from capturing his face. Thus, all the credit is given to Lestrade instead.

The credits flash by and consist of newspaper headlines detailing Holmes and Watson's exploits.

The scene now cuts to Baker Street, where Watson is treating an elderly patient.

As he dresses, the patient asks about Watson's plans to move his medical practice to a new headquarters. Watson confirms that he is moving, and that he hopes to have the touch of a woman around the place soon. The patient congratulates him on his (potential - as Watson hasn't proposed yet) nuptials, before nervously asking if Holmes is moving too. Watson says no, but is promptly interrupted by several loud blasts that send both men ducking for cover.

The patient leaps up and says that the blasts must be gunfire, but Watson soothes him and tells him that Holmes is probably hanging a picture with nails and hammer. Watson ducks out to check on the commotion, and is met by their housekeeper Mrs. Hudson (Geraldine James). She tells Watson that Holmes is in a mood, and she hopes that he can calm Sherlock down. At this point, the elderly patient comes out and is about to talk, when there's the sound of gunfire again. Watson tells Mrs. Hudson to get the patient a cup of tea, and he'll go see to Holmes himself. He also asks Mrs. Hudson to bring some food to cheer Sherlock up.

When Watson walks into Holmes's study, the entire room is dark.

Watson comments into the darkness that he knows Holmes bored, as it's been awhile since he's had a case. Holmes remarks that he's trying to figure out a way to silence the sound of gunfire, and Watson sarcastically retorts that it's clearly not working. As Watson talks, he goes around opening up the blinds in the room, which causes Holmes to groan painfully.

Watson starts rifling through Holmes's mail and offers him prospective cases to consider. Holmes flippantly solves all of them without a second thought. Watson also points out that Holmes is in the papers again, as Lord Blackwood is about to be hanged. We also learn that Watson will be the attending physician at the hanging, as he considers it a good away to conclude his final adventure with Holmes.

Mrs. Hudson comes in with tea and snacks, points out that the family bulldog is lying immobile on the floor, saying that Holmes has killed the dog, again. Watson hurried over to check on the animal, and asks Sherlock what he's done to the dog now. Holmes nonchalantly says he was just testing out a new anesthetic.

Nothing seems to be cheering Holmes up, so Watson throws down the mail and tells Holmes that he needs to get out of the house. He tells Holmes that he's going to join Watson and his future fiancée for dinner at a London hotel. Holmes begrudgingly agrees.

We cut to the hotel and pan through a crowd of elegantly dining men and women.

Holmes is sitting alone at a table, well dressed but looking incredibly uncomfortable. He checks his watch several times before Watson and Mary Morstan (Kelly Reilly) shows up. They chitchat, and Holmes' deductive powers come up. Mary shows some suspicion at Holmes' deduction skills. He points out several details about Watson simply from his walking stick, indicating that he is a decorated army veteran of the Afghan Wars. Mary asks Sherlock to analyze her, over Watson's objections. He points out that she's a governess and has been engaged once before, but likely broke off the engagement because the fiancé wasn't wealthy enough for her. By this point Mary is starting to be come increasingly uncomfortable with Holmes' comments, but Holmes doesn't notice her discomfort or Watson's warnings. He just continues rambling on. He also adds that she's probably trying to do better this time around - e.g. finding a doctor to wed. Mary's extremely offended by his comment, and tosses a glass of wine in his face. She then tells him that everything he said was true, but her first fiancé died. She then gets up to leave, throughly upset by Holmes' rudeness, and is followed by Watson. Holmes remains at the table and has his dinner, alone.

Cut to Holmes fighting a much larger man in a boxing ring. He's getting pummeled by the larger man and seems to be losing. He's suddenly distracted by the appearance of a white handkerchief at the side of the ring with the initials "IA." He scans the room and sees Irene Adler (Rachel McAdams), who then winks at him. Holmes makes to leave the rink - to the great disappointment of those cheering him on - but stops when his opponent spits on him.

Using the deductive logic we saw earlier, Holmes figures out how to use the handkerchief and some well-calculated moves to take out opponent. He carries them out with blinding speed to the shock and surprise of everyone in the room. When the opponent hits the ground, the entire room falls silent in shock, and someone actually says, "Where did THAT come from?" Holmes looks around, and realizes that Irene's gone. He takes the money from a bookie and leaves.

Over at Scotland Yard, the prison guards are trying to deal with a potential riot. Lord Blackwood has caused a guard to come down with seizures, and no one wants to be around him for fear of his black magic. One of the braver guards asks him what he wants, and he says that he wants to talk to Holmes. It's his final request.

Cut to Watson walking up the stairs in a rundown building. He goes into a room, where we see Holmes under the influence of cocaine, strumming away at a violin. Holmes greets Watson, and gestures to a bottle with flies.

He tells Watson that when he plays a certain pitch, the flies will fly in a counterclockwise direction. Watson sighs and asks him how long it took Holmes to catch the flies, and Holmes admits about six hours or so. Watson raises his eyebrows and goes "Really? What if I do this...?" and opens up the lid, letting all of the flies escape. Watson then tells Holmes to get up and get decent, as Blackwood has requested to see him.

Watson brings Holmes to the prison. On the carriage ride over, Holmes attempts to engage Watson in conversation, but Watson rebuffs him. Finally, Watson punches Holmes in the nose and tells Sherlock that he had already known about Mary's previous fiancé. They bicker for a while, and finally arrive at the prison.

Most of the guards are afraid of getting too close to Lord Blackwood, so Holmes tells them that he can find his way out own his own. Blackwood greets him, and tells Sherlock that Blackwood isn't done killing just yet. He's planning on killing three more people, and there's nothing Holmes can do about it. He also tells Holmes that trying to stop him will be an extremely futile gesture. Holmes ignores him, and makes several remarks about Blackwood's upcoming hanging and makes offhand comments about how even though Blackwood was cunning, his devious plans were going to come into an end. Finally Holmes leaves without paying much thought to Blackwood's warnings.

Cut to a British court where Lord Blackwood is sentenced and hanged. After the hanging, Watson feels for a pulse, and then legally declares him dead.

Cut to Holmes sleeping in his study. We see a woman's gloved hand cracking walnuts, which wake Holmes up. We discover that Irene Adler is in the study with Holmes, and she's brought him food from her travels. It is obvious the two has met before. Holmes looks rather unnerved and begins hastily straightening up the place; including slamming a portrait of Irene that he has on his desk facedown.

The two of them banter for a bit, and there's obviously some kind of romantic chemistry there. Holmes wryly comments on her con artist talents, and Irene just shrugs it off. She tells him that she needs him for a case, and hands him an envelope with information and money. She then gets up to leave, but not before putting Holmes' portrait of her into an upright position again. Sherlock strums at his violin and watches her leave.

Irene runs into Watson at the door, and greets him. Watson seems rather stunned, but doesn't say anything. We follow Irene down the street, until she gets into a carriage with a figure sitting in the shadows. She tells him that she's sure Holmes will agree to take the case. Their conversation is interrupted by a street bum who lurches up to the car, but is quickly scared off by the shadow-y man's wrist pistol.

Cut back to Baker Street, where Watson chastises Holmes for falling for Irene. Holmes denies this, but Watson continues to tease him about this. Watson reveals that the case Irene wants Holmes to solve involves him finding a ginger dwarf. He makes some jokes about Irene's taste in men, and asks Holmes what he was doing. Holmes starts to explain, and the story flashes back to what Holmes was doing while Irene was walking down to the carriage. Watson is going up the stairs when he sees Holmes trying to open a window. He tries to ask Holmes what he is doing, but Holmes is obviously in a hurry, and he doesn't explain anything to Watson. Holmes jumps out the window and crashes. Watson sighs and closes the window, ignoring Holmes. Holmes runs down the allyways, following Irene. Along the way, he picks up some disguises, and finally reveals that the street bum was actually he. He also comments about the man in the carriage, claming that Irene is scared of him. Watson is surprised by this, saying that Irene isn't scared of anyone.

As they're talking, a constable from Scotland Yard comes in and tells them that Lord Blackwood has apparently risen from the grave. Holmes wants Watson to come with him, but Watson says he needs to visit with Mary. Holmes obviously wants Watson to come with him, so he berates Watson for not caring about his reputation, saying that no girl wants to marry a man who can't tell if a man is dead or not. Watson finally agrees to go. They're taken to the cemetery to meet with Lestrade, where the limestone outside of Blackwood's mausoleum has shattered. Holmes examines the scene and licks a piece of the stone and waits as Lestrade and his men bring the coffin out. Once they open the coffin, the body inside turns out to be that of Irene's red-haired man.

Holmes examines the body, and declares the man probably died about twelve hours ago. He also takes the man's watch without anyone noticing, and then tells Lestrade he'll follow up. Holmes and Watson leave the cemetery.

Cut to Watson and Holmes walking down a London street, where Holmes discusses the initials scratched on the watch. Holmes tests Watson's deducing skills by having him explain the marks. Watson deduces that they're the markings of pawnbrokers, and they'll be able to obtain the man's last address from the pawnbroker.

Outside the pawnbroker, Watson is approached by a gypsy woman who claims she knows about him and Mary. He tells the woman to tell him his fortune, and she tells him that marriage is a bad idea, as it'll consist of Mary growing fat, print wallpaper and doilies. Holmes solemnly echoes everything she says, and Watson realizes this was a huge setup on Holmes's part. He asks if Holmes has no shame, and then - just to spite Holmes - buys an engagement ring for Mary on the spot.

After Watson purchases the ring and Holmes has obtained the red dwarf's address, Holmes makes to go in and examine the building. Watson tells him he can't follow, as he has a dinner planned with Mary's parents. Holmes looks disappointed but understanding, and goes in alone. Watson stands in the street for a minute before sighing to himself, and follows.

Holmes is in the middle of picking the lock on the red dwarf's door - he has a utility belt that made me think of Batman's - when Watson just kicks the door in. They greet each other cheerfully, and go into the room.

The room is in shambles, filled with medical equipment and experimented-on animals. Watson finds a piece of paper with Lord Blackwood's watermark - effectively linking the red-headed dwarf to Blackwood - and Holmes snips the tail off of a experimented-on (and dead) rat.

The duo also notices a plate with some kind of melted substance and honeycombs. Holmes is right in the middle of saying that everything fits in with what he's been thinking, but there was one smell he couldn't identify. Just as he's talking, two men eating caramel apples (the scent that Holmes was smelling) appear in the doorway, and Watson calls Holmes's attention to them.

Holmes notes that they're carrying canisters in their hands, and asks the men if they're here to burn down the building. They smile sinisterly and say yes, and then call out for their colleague - an extremely large man who only speaks French.

A brawl between Watson, Holmes and the three men begin in earnest. Watson takes on the two associates, while Holmes takes on the French man. As they fight, Holmes pauses to catch his breath, and ask for a moment, and the French man shrugs and politely says it's not a problem.

The fight comes to a head when Holmes discovers an electricity-powered rod amongst the redheaded dwarf's things. He wields it at the French man, and it zaps him with enough force to throw the man backwards. Even though Holmes admits that he doesn't know how it works, he chases the French man out of the room with it. Watson is left to finish off the two associates, but not before accidentally dropping Mary's engagement ring.

Holmes chases the French man down the street and into a London shipyard. There's a half-finished boat in the yard, and the men all look up in interest as Holmes threatens to zap the man. He asks the man who he works for, and the French man responds, "You know who", before reaching over and crushing the rod. Now defenseless, Holmes can only run.

The two men duke it out in the shipyard as Watson follows them in. (This is the scene you see in the trailer where the French man has the larger hammer and Holmes has the smaller one). Through some miscalculations on Watson's part, the moorings for the boat are released and the half-finished boat falls into Thames. The scene ends with Watson - having dived to save Holmes from the moving boat - both looking at the half-sunken ship, and Holmes asking "What have you done, Watson?"

Cut to Watson and Holmes sitting in an outdoors holding pen. It looks like a drying out tank for minor criminals. Watson complains to Holmes that all he wanted to do was eat dinner with Mary's parents, and it becomes a full-on rant about Holmes's various bad habits. (It's the scene in the trailer where Watson complains about Holmes's mess). Holmes tries to deflect Watson, and their argument really seems like that of an old-married couple.

Just as Watson's about to really get going, a police guard calls Watson's name and tells him his bail has been posted. We see Mary standing outside and smiling. Watson gets up and Holmes follows, but Holmes is told that bail has only been posted for Watson. As the gate slams behind Watson, one of the other criminals being held tells Holmes that he better get out soon, as the criminals are getting "hungry".

Scene cuts to a large group of people surrounding something we can't see. The guards are worried it might be a riot, but it turns out to be Holmes sitting down with the criminal from earlier, cracking jokes. The crowd laughs uproariously, before a guard steps in to tell Holmes that his bail has been posted. When Holmes asks who posted the bail, the guard just says that Holmes has friends in high places. We see a rich-looking carriage in the distance, where a hand beckons to Holmes. He steps in, and is told he has to be blindfolded.

The scene cuts to the interior of a large mansion, and Holmes's blindfold is taken off. Standing in front of him is Sir Thomas (Edward Fox) and another associate. They apologize for blindfolding Holmes, saying they needed to protect their location. Holmes scoffs a little, and gives a turn-by-turn account of where they are, simply based on observations using his other senses. He then notes the ring on Sir Thomas's finger, and asks what he can do for The Temple of Four. It's at this point that the Home Secretary Lord Coward (Hans Matheson) steps into the room as well.

The Temple of Four is a secret society similar to The Illuminati and the Freemasons who practice magic for good. They tell Holmes that Lord Blackwood was once a member, but they're having trouble controlling him. They want the situation resolved, and are willing to put everything they have at Holmes's disposal. Lord Coward tells Holmes that as he is the Home Secretary, he has control of the police force.

Sir Thomas tells Holmes that the key to Lord Blackwood's power is in a book of spells. He hands a book to Holmes who flips at it disinterestedly. Thomas says he knows that Holmes doesn't believe in magic, but it's important.

Holmes says he'll help, but not because he wants their resources. He's genuinely curious about the situation. He also points out that Sir Thomas is Lord Blackwood's father, based on recognizing similar traits in their faces. Sir Thomas seems stunned, and says that very few people know of the relation. Sir Thomas conceived Lord Blackwood with one of the women used in their rituals, and Blackwood has been evil since his youth. Holmes says that given that everyone Blackwood was close to has been killed, he wants to know how long Sir Thomas can last. The three men look at each other anxiously as Holmes leaves.

Cut to Irene Adler's hotel. She's in a towel, and walks from the bathroom to the door. She opens the door and finds Sherlock attempting to pick the lock. She greets him, and hands him a bottle of wine saying, "Here's something you might be able to open."

As she changes behind a screen and with her back to Holmes, Holmes confronts her about the redheaded dwarf being found dead. We can see by her expression that she's very troubled by this news, but she plays it off for Holmes. Holmes urges her to flee, and she invites him to come along. He says he can't, but tells her that she has to go or he's going to put her in protective custody.

(Holmes is always jumpy around Irene, and it's a combination of being attracted to her and wary of what tricks she might have up her sleeve. It's very amusing/endearing and Downey Jr. does it well).

Holmes confronts Irene about the man in the carriage, remarking that he must be a professor given the chalk on his collar. Irene seems completely non-plussed that Holmes has followed her. We understand that this is a game of chase for both of them, and will always be that way.

Irene pours two glasses of wine and hands Sherlock one. He gulps it down, and immediately begins to feel dizzy. He realizes then that the wine was drugged. Irene chidingly tells him that he shouldn't have refused to come along, and pulls him onto the bed. He passes out.

Cut to Sir Thomas's mansion. He's in the bathtub, relaxing. He hears a noise, looks around but dismisses it. Suddenly, the water starts bubbling, and we see Lord Blackwood sitting in the background. Sir Thomas tries to turn the water off, but fails. Lord Blackwood pushes Sir Thomas's hand into the water, and also takes Thomas's ring. He dies while Blackwood watches.

Cut back to Irene Adler's hotel room. Holmes has been handcuffed to the bed, and has pillow covering his genitals. Irene has left the key for the cuffs behind the pillow. A maid comes in and Sherlock tells her that the "key to his release" is behind the pillows, and the maid shrieks and runs out of the room.

Cut to Holmes sitting in a carriage, retelling the story to the constable who had fetched him to Lord Blackwood's gravesite earlier in the film. The constable finds the whole thing extremely amusing, and says it's a good thing that the maid was offended enough to call the police, as it helped Sherlock out of the situation quicker.

They pull up to Sir Thomas's mansion, and they begin their examination of the body/murder site. Holmes asks why the water's been drained, and the constable says it was out of respect. Holmes sits down and sort of laughs at Scotland Yard's incompetence. He tells them to look for a bath powder while he examines the scene.

After the last constable leaves the room, Sherlock begins tapping on walls, and finally finds a latch that allows him to open up a hidden door. Behind the door is a small space that magic tools/symbols/etc. Holmes rifles through the items and picks up two skulls and a book of spells, which he slips into his coat pocket. As the constables come back into the room, he asks them if they've found the powder. They say yes and he leaves.

Cut to a dark London street, and a man wearing a cape and walking briskly. As he taps on the door of a non-descript house, it appears to be raining. He goes inside and is revealed to be Ambassador Standish (William Hope), the ambassador to the United States.

(As a side note, Standish has a really odd accent. It tries to be American, yet it doesn't quite work).

Standish is greeted by Lord Coward and other members of the Order, who inform him that Sir Thomas is dead. Coward then tells him that they're voting on a new leader, and suggests Lord Blackwood. Standish seems stunned, but Coward says that this is the natural order of things. Blackwood (according to Coward) is powerful enough to make Britain regain its past glory, including winning back to the US. Blackwood appears, and says that the US is currently embroiled in the Civil War and is ripe for the taking. He then sits down in the leader's chair.

Standish says that he won't stand for this, and pulls out a gun to fire at Lord Blackwood. As he fires, Standish bursts into flame, which shocks the other members. Standish leaps out the window and hits the ground, while Coward urges the other members to drink to their new leader.

Cut to Watson packing up his medical studio. Holmes sticks his head in and asks if he can use Watson's study, now that it's no longer occupied. Watson seems a little hurt but agrees, and Holmes carries in a body. It's from one of the ruffians from earlier who tried to beat up Watson and Holmes.

They examine the body, and try to figure out where the man has been in the last twenty-four hours. They determine that he was working out of a meat factory near the Thames, a lead Holmes wants to chase down immediately. Holmes tells Watson he doesn't have to come, but deliberately leaves his pistol on the table. (It's a callback to the beginning of the movie, when Holmes forgot his pistol and Watson brings it to him). Watson sees the pistol, sighs and follows.

Cut to a boat on the Thames. Holmes and the boat owner are laughing uproariously while Watson's struggling with manning the boat. Watson complains that they're not doing anything, but Holmes and the boat owner just laugh at him.

Cut to the men docking near the previously mentioned factory. Holmes and Watson go inside, and the setup is very similar to the redheaded dwarf's place. There's a lot of scientific equipment, and a biblical quotation that refers to the end.

As Holmes and Watson stalk around, they notice a row of pigs hanging on a line, ready to be chopped into pieces. They're interrupted by Lord Blackwood's voice, who says that he warned Sherlock all of this would happen. Sherlock and Watson back up against the wall with their weapons brandished, but they can't figure out where the voice is coming from.

We suddenly see Blackwood's face in a crack in the wall behind Holmes and Watson, and both men jump, turn around and shoot. However, Blackwood manages to get away, but not before 1) saying that "she" followed Holmes and Watson and 2) setting off flames. Cut to a bound and gagged Irene Adler hanging from the pig line, surrounded by flames. Watson cautions Holmes that, "this game is going to hurt".

Holmes wraps himself in a blanket and races towards Irene. He throws the blanket around Irene, trying to protect her from the flames. At the same time, Watson begins fiddling with equipment to get the flames to stop. He manages to stop the flames, but the line is still headed towards the blades.

Holmes sees a box of scraps, reaches up and throws the scraps in the gears of the line, trying to jam it. It works for a couple of seconds, but the scraps move and the line continues to move. Holmes tells Watson to prop Irene up, while he tries to figure out what to do. Watson races over, and Holmes grabs a saw and tries to hack away at the chains binding Irene to the line. It doesn't work.

They're only seconds away from the animal-slicing saw now, and Holmes sees a steam pipe. He tells Watson to turn it on, and he effectively overloads the pipe and brings the line crashing down. Irene is saved from the saw, only seconds away from being chopped up. Once freed, she hugs Watson and Holmes, also leaning to kiss Holmes on the cheek.

Watson goes after Lord Blackwood with Holmes following close behind. As Watson runs, he's too distracted by the boat leaving, and accidentally trips a line. He turns around to see Holmes behind him, and yells at Holmes to stop. Unfortunately, the line has already been tripped, and a series of explosions rips through the building. Watson and Holmes are separated by blasts, so Holmes grabs Irene and tries to shield her to the best of ability. The explosions go on for some time, and Holmes finally blacks out.

When Holmes finally comes to, the constable from earlier (the one that summoned him to Blackwood's grave and escorted him to Sir Thomas's murder scene) is shaking him. He tells Holmes that Lord Coward has utilized his powers and issued a warrant for Holmes's arrest. He also informs Holmes that Watson's doing okay, but Holmes must flee immediately. Holmes gets up and begins to run.

We cut to Irene Adler dressed and about to board a train. She asks a conductor if the train is delayed, and he assures her it is not. She gets into her car, and we see the shadow figure from earlier sitting in a corner, reading a newspaper. He tells her that the train will leave when he wants it to; He also chides her saying that he hired her to manipulate Holmes's feelings for her, not to have her succumb to them. Irene gulps.

Cut to a doctor leaning over Watson in a hospital ward. Watson's asleep, and we can see that he's severely injured. We see Mary approach the bed and ask the doctor how Watson's doing. The doctor hastily excuses himself, and Mary follows, asking if that's "the best he can do." We get a close-up and see that the doctor is actually Holmes in disguise.

Holmes looks guilty and anguished, but Mary gently assures him - without ever acknowledging his identity - that Watson wouldn't have gotten involved if he didn't want to. He saw the whole thing as an adventure. She tells Holmes that everything's going to be okay, but he needs to fix it.

Cut to Holmes sitting in the opium room from earlier, thinking over the situation. He pulls out the bones he collected from Sir Thomas's, along with the spell book. Holmes decides that the only way to truly understand the situation is to understand the magic, and attempts to create one of the spells. His mind wanders in a daze, and he passes out.

Cut to Holmes on the bed, waking up to Irene staring down at him. She greets him, and then we see that Watson is sitting in the room as well. Watson comes over to sit on the bed with him, and they have an awkward moment of not looking each other, grumbling that they're glad the other is okay. (It's very much another bromance moment). Irene just studies them with amusement.

Watson asks about Holmes's recreation of the magic (there's really detailed pentacles and animals drawn all over the floor), and Holmes explains that it allowed him to understand Lord Blackwood's next move.

* He explains that based on the spell book, spell practitioners will always have a drawing of a pentacle and a cross in the pentacle.