In the novel, Holmes is approached by a young governess named Mary Morstan. Her father, Captain Arthur Morstan, has been missing for ten years, and once a year for the last six years she has received in the mail a valuable pearl from an anonymous benefactor. Holmes discovers that Captain Morstan's old friend Major Sholto, who knew Morstan from Army service, died not long before Miss Morstan started receiving pearls. They soon meet with Sholto's son Thaddeus, who reveals to them a wild tale of a mysterious treasure stolen by his father, who also concealed the accidental death of Capt. Morstan. Then Thaddeus's brother is murdered, and the plot thickens further.
For the 1932 film adaptation, see The Sign of Four: Sherlock Holmes' Greatest Case.
This page is for tropes specific to the novel. For general tropes about Sherlock Holmes, see the Sherlock Holmes page.
- Adorkable: Watson, whenever he is around Mary Morstan.
- Artificial Limbs: The villain, Jonathan Small, has a wooden leg.
- Aerith and Bob: Sherlock Holmes uses the four names on the titular pact to deductively identify Jonathon Small, the sole English name on the pact, as the murderer of Bartholomew Sholto.
- Big Bad: Jonathan Small
- Bilingual Bonus: On the final pages, Holmes quotes a distych by Goethe (No. 20 Der Prophet from the Xenien Goethe wrote in collaboration with Schiller in 1796 against their literary colleagues.):'Yes,' he answered, 'there are in me the makings of a very fine loafer, and also of a pretty spry sort of fellow. I often think of those lines of old Goethe:—Schade, dass die Natur nur einen Menschen aus dir schuf,Denn zum würdigen Mann war und zum Schelmen der Stoff.note '
- Bittersweet Ending: Watson and Mary find happiness, but she doesn't get the treasure, which is at the bottom of the Thames. (And it's one of the bitterest endings for Holmes's personal life, despite the fact that he seems to get over the upheaval in later stories.)
- Blow Gun: Tonga uses poison blow darts.
- Book-Ends: Begins and ends with Holmes injecting himself with a seven-per-cent solution of cocaine.
- Captain Obvious: a tongue-in-cheek example:
- Chase Fight: The conclusion of the case is marked by a thrilling boat chase between the good guys and the bad guys. The "fight" part (sort of) comes in when Tonga fires one of his poison darts at the good guys, misses, and gets shot by Watson for his troubles.
- Functional Addict: This novel introduces Holmes's cocaine habit. While his habit is clearly serious, Holmes has no problem putting the cocaine aside when he gets a case, and doesn't shoot up again until the case is over and he is once again bored.
- Go Out with a Smile: The poison from Tonga's blowdarts, being derived from strychnine, inflict this on Bartholomew Sholto.
- Gorgeous Period Dress: Watson gives a rather meticulous description of Mary Morstan's dress.
- Good Old Fisticuffs: A professional boxer remarks that Holmes could have quite a career in the ring.
- His Name Is...: Major Sholto is interrupted, and promptly dies, just as he's about to tell his sons where the treasure is.
- Hypochondria: Thaddeus Sholto has this, which greatly irritates Dr. Watson.
- Hypocritical Humor: Athelney Jones lectures Holmes about the importance of facts over theories when he'd arbitrarily decided that Thaddeus had murdered his brother over the treasure before even entering the crime scene, much less examined it for evidence.
- Locked Room Mystery: Bartholomew Sholto is found dead inside a locked room.
- Love at First Sight: Watson falls for Mary Morstan pretty much instantly.
- Never Found the Body:
- The body of Tonga was lost in the Thames. Perhaps because it's an Unbuilt Trope, there's no suggestion that he isn't really dead.
- Very much averted in Small's flashback. The reason why Small and his comrades end up in Hope Town is because the body of the rajah's servant is found.
- No MacGuffin, No Winner: When he realizes he can't get away, Small throws the treasure in the river rather than let anyone else have it.
- The Mutiny: The Sepoy Mutiny of 1857, recounted by Small in his Whole Episode Flashback, which started a series of rebellions in India. The resulting chaos led to Small and his gang stealing a large treasure that a rajah was trying to send to safety in a British fort.
- Not with Them for the Money: Watson to Mary Morstan—to the point where he resolves not to even bother wooing her if the money Holmes is searching for turns up, not wanting to be thought of as a Gold Digger. He doesn't tell her his true feelings until the treasure box is found, empty.
- Police are Useless: Athelney Jones arrests pretty much the entire Sholto household for being connected to Bartholomew's murder on no evidence whatsoever (correctly catching one accomplice in the murder by sheer luck), causing Watson to comment to Holmes that they're lucky they didn't get arrested as well. The only thing he does that actually helps solve the case is provide Holmes with a steam launch to run down Small's boat in the finale.
- Running Gag: Watson twice confuses two terms in his storytelling and medical advice (shooting a rifle in the face with a tiger cub and recommending plenty of strychnine but cautioning against excessive doses of treacle) and only being informed of his error by Mary Morstan or Holmes after the narrative.
- Seadog Peg Leg: Jonathan Small is a former soldier who lost his leg to a crocodile while serving the British army in India and replaced it accordingly. He has also sailed throughout the world, although that happened after losing his leg.
- The "The" Title Confusion: It was originally serialized as The Sign of the Four, but many subsequent serializations (and its initial publication into a novel) used The Sign of Four instead. The four-word title remains the more popular choice. Note that in the actual story, most characters call it by the five-word name.
- They Have the Scent!: Holmes employs the mongrel dog Toby to track down Jonathan Small, who had accidentally stepped in some creosote. Temporarily subverted when Toby gets his scent trails crossed and leads them to a barrel of the stuff at a construction site.
- Title Drop: Jonathan Small signs his notes and treasure maps with "the sign of the four"—that being him and his three fellow conspirators who first stole the treasure.
- Unexpected Inheritance: Mary finds out that she stands to inherit an enormous fortune if Holmes can retrieve the treasure that her father had a 1/10 share off.
- Whole Episode Flashback: Jonathan Small confesses after he's caught, and tells a long story towards the end in which he explains how he came to acquire the treasure and how Morstan and Sholto became involved in the plot to retrieve it.
- You Do Not Have to Say Anything: Apparently in 1890 it was it is my duty to inform you that anything which you may say will be used against you.
- Adapted Out: In most adaptations, the Rajah's servant set to secretly watch over the one escorting the treasure and then alerting the authorities in Agra about his disappearance and then the subsequent discovery of his corpse is left out. Instead most adaptations merely state the body was discovered, because the Four decided to give him a Due to the Dead by burying him (cremating the body according to Sihk custom being impossible without attracting attention) instead of feeding the corpse to the jackals lurking outside the fort's ditches. Watson sums it all nicely in the Granada adaptation:Dr. Watson: A body not burned in India is soon discovered.