7 Canonical References in The Sign of Three

Spoilers ahead—read at your own risk!


“The Sign of Three” is one of the most canon-heavy episodes of Sherlock to date, and there are many more references than I’m listing here. This is just a short exploration of some of my favorites.

  1. Clever Mary

“The Sign of Three” had numerous obvious references to The Sign of Four, the canonical novel by Sir Arthur Conan Doyle in which Watson and Holmes meet Mary Morstan, and Watson falls in love with her.  One of my favorites, which went through the episode, was the strong indication of Mary’s intelligence. During the wedding planning scenes, Mary remarks that she can tell when Holmes is fibbing, even when Watson can’t. She also has several conversations with Sherlock in which she relates to him on a level that shows her awareness of his positive qualities and his awareness of hers.

In The Sign of Four, upon being told that Watson intends to marry Mary Morstan, Holmes remarks, “I think she is one of the most charming young ladies I ever met, and might have been most useful in such work as we have been doing. She had a decided genius that way: witness the way in which she preserved that Agra plan from all the other papers of her father.” During this same conversation, Holmes says that he cannot congratulate Watson on marrying Mary and taking away the potential for her to become a detective.

In “The Sign of Three,” Holmes also speaks about not (initially) being able to congratulate Watson, but ultimately does so, basing his congratulations on the fact that the Mary found in Sherlock is worthy, just as Doyle’s version was.

  1. Mycroft’s Weight Issues

One of the humorous through-lines in Sherlock is Mycroft Holmes’s ever-present battle with his waistline. In “The Sign of Three,” we see him exercising, and Sherlock intimates that this is something he does regularly.

The creators of Sherlock have updated the concepts of drug use and smoking to be friendlier to a modern context, and this concept has been treated in a similar way. During “The Adventure of the Greek Interpreter,” Doyle has Watson describe Mycroft this way, “Mycroft Holmes was a much larger and stouter man than Sherlock. His body was absolutely corpulent, but his face, though massive, had preserved something of the sharpness of expression which was so remarkable in that of his brother.”

To update Mycroft for the modern, fitness-obsessed world (and connect Mark Gatiss with one of his finest performances ever), the writers of Sherlock have let him lose the corpulence but continue to engage in a very human struggle with his weight.

  1. The Speech

Sherlock’s Best Man toast is undoubtedly iconic in the canon of Sherlock, and it made numerous references to stories from the Doyle canon. In particular, at the beginning, when he addresses his disdain for love and marriage, he paraphrases Watson’s description of him from “A Scandal in Bohemia,” which reads, “All emotions, and that one particularly, were abhorrent to his cold, precise but admirably balanced mind. He was, I take it, the most perfect reasoning and observing machine that the world has seen, but as a lover he would have placed himself in a false position.”

Of course, Holmes’s actions in “The Sign of Three” belie his claims of being without love, just as his actions throughout the canon, and particularly post-Great Hiatus, give lie to Watson’s assertions about him.

  1. Mary’s Maid of Honor

“The Sign of Three” features Holmes enjoying an awkwardly gentle flirtation with Mary’s Maid of Honor, something it would have been difficult to imagine him doing at the beginning of the series, but which jives nicely with his character development in Series 3.

Similarly, in Doyle’s “The Lion’s Mane,” one of the few stories narrated by Holmes himself, he describes a woman named Maud Bellamy, “She listened to a short account from my companion, with a composed concentration which showed me that she possessed strong character as well as great beauty. Maud Bellamy will always remain in my memory as a most complete and remarkable woman.” It would be difficult to imagine the protagonist of A Study in Scarlet saying this, but Doyle did not make Holmes a static character.

Like a real person, the canonical detective grows and changes, and part of this change includes a softening toward people in general and women in particular. The writers of Sherlock have chosen to show this development in a similar way.

  1. Sholto

In Doyle’s The Sign of Four, Major Sholto is a friend and army colleague of Mary Morstan’s father. The character and circumstances are very different from those in “The Sign of Three,” which provides an entertaining puzzle for canon lovers watching Sherlock who can’t help wondering whether or not his actions will mirror those of the original Sholto, much like in “The Hounds of Baskerville,” which similarly used canonical characters in new ways.

  1. Holmes and Children

One of the most humorous sequences in “The Sign of Three” concerns Sherlock coaxing and bonding with a young boy named Archie, who ends up entirely taken with the detective and his gruesome occupation. Giving Holmes the ability to connect well with children is entirely Doylean.

The Sign of Four contains a chapter named for the Baker Street Irregulars, the group of children Holmes employs, and generously compensates, for prowling the streets to gain information for him. It’s obvious from Watson’s brief description of Holmes’s relationship with the children that they adore him and that he, in turn, is very fond of them.

Sherlock has largely used Holmes’s homeless network as a stand-in for the Irregulars, but it’s nice to see a reference to the detective’s canonical ability to enchant the younger generation. Interestingly, “The Sign of Three” also features Sherlock promising Archie that he will ask a grownup about something—indicating that he thinks of himself as more of a child than an adult, echoed in his final words to Mary and John at the end of the episode.

  1. C.A.M.

Mary and John receive a wedding telegram from someone with the initials C.A.M., which is the set of initials that belong to the antagonist of Doyle’s “Adventure of Charles Augustus Milverton.” What exactly this means for Sherlock’s characters we have yet to discover.


The Detective, The Woman and The Winking Tree: A Novel of Sherlock Holmes is available from all good bookstores and e-bookstores worldwide including in the USA Amazon,Barnes and Noble and Classic Specialities – and in all electronic formats including Amazon Kindle , iTunes(iPad/iPhone) and Kobo.

The Detective and the Woman: A Novel of Sherlock Holmes is available from all good bookstores and e-bookstores worldwide including in the USA Amazon,Barnes and Noble and Classic Specialities – and in all electronic formats including Amazon Kindle , iTunes(iPad/iPhone) and Kobo.

10 thoughts on “7 Canonical References in The Sign of Three

  1. Pingback: The Sign of Three, Sentiment, and Sir Arthur Conan Doyle | Girl Meets Sherlock: A Holmesian Blog

  2. Pingback: 7 Canonical References in His Last Vow | Girl Meets Sherlock: A Holmesian Blog

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