Netflix detective story Enola Holmes introduces Millie Bobby Brown as the younger, brilliant sister of famous detective Sherlock Holmes (Henry Cavill). While several characters from Arthur Conan Doyle's classic Holmes stories appear in the film, like Inspector Lestrade (Adeel Akhtar) and Mycroft Holmes (Sam Claflin), a conspicuously absent figure is Sherlock's faithful friend and the narrator of his stories, Dr. John Watson.
In Nancy Springer's The Case of the Missing Marquess, the book upon which Enola Holmes is based, John Watson is mentioned briefly as the author of A Study in Scarlet (the first of Doyle's Sherlock Holmes novels). The film, however, goes out of its way to suggest that John Watson hasn't yet entered Sherlock's life. When Enola turns up at the Basilwether estate and claims to be Sherlock's assistant, Inspector Lestrade counters that Sherlock Holmes has never had an assistant and always works alone. When Sherlock visits Edith (Susan Wokoma) at the tea shop, she scathingly observes that he has, "no wife, no friends, just a strange occupation."
In the montage where Enola recaps her brother's accomplishments, newspaper clippings refer to him as a mysterious "young" detective, and Cavill certainly brings a youthful energy to the role. Between the above clues about Sherlock leading a lonely life, the characterization of him in the film and the year that Enola Holmes is set in, we can deduce a simple explanation for John Watson not being in the movie: Sherlock hasn't met him yet.
Enola Holmes Is Set Three Years Before A Study In Scarlet Was Published
Enola's introduction and various dates on newspapers throughout the film pinpoint the year Enola Holmes is set in as 1884. Though A Study in Scarlet is actually set in 1881, after John Watson's return from the Second Anglo-Afghan War, the novel wasn't published until 1887. Given that Enola Holmes already takes some major liberties with Sherlock Holmes canon, it wouldn't be much of a stretch if the film changed the year of Sherlock and John's first meeting to some time after 1884. This leaves open the opportunity for a future Enola Holmes sequel to properly introduce John and to give him a more central role in the story. Since Enola Holmes is busy setting up its titular character and her story, there probably wouldn't have been room for much more than an unsatisfactory cameo for Watson in it.
One of Springer's Enola Holmes books actually does focus on John Watson. In The Case of the Bizarre Bouquets, Watson goes missing and Enola must solve the mystery of where he's gone. The book would make for a compelling story if Netflix were to greenlight Enola Holmes 2. The sequel could jump forward in time to find Enola with her own properly established detective business, and Sherlock having made his first real friend. In the meantime, the door for fan-casting a new John Watson is wide open.