Sherlock Holmes Is Officially Switching Main Characters

Published Sep 15, 2026, 4:47 PM EDT Adrienne Tyler is a movies & TV features writer, with a focus on horror. She has written for Netflix, FanSided, & more. She was a regular guest on the Netfreaks podcast and was a YouTuber at some point. Guillermo del Toro said “hi” to her once. The stories of Sherlock Holmes have their main characters well established, but the classic detective is now switching main characters, and it's for the better. Created by Sir Arthur Conan Doyle, Sherlock Holmes is the most famous detective in literature, and his enduring popularity has led to many adaptations to all types of media for decades. Many Sherlock Holmes adaptations and shows inspired by him are now among the best detective TV shows of all time, including some modern ones. The most popular and successful modern adaptation of Sherlock Holmes is the BBC's Sherlock, which brought the Great Detective and company to modern-day London, as did its competitor, the CBS’ Elementary. Despite their modern setting, both Sherlock Holmes shows stayed true to the basic elements of Conan Doyle's stories, most notably Holmes and Watson as main characters, with Moriarty as the big villain. However, that has now changed with Prime Video's Young Sherlock. Inspired by Andrew Lane's book series of the same name, Young Sherlock gives a twist to the Great Detective by taking the audience back to the Victorian Era to meet Holmes before he became the famous detective everyone now knows. This obviously prompted other changes to Holmes and other characters, most notably his companion, as John Watson arrived in Holmes’ life many years later, so Young Sherlock had to give him a different and surprising sidekick: James Moriarty (Dónal Finn). Young Sherlock Replaces Watson With Moriarty (For Now) As the title says, Young Sherlock follows a younger version of the Great Detective, played by Hero Fiennes Tiffin. This 19-year-old Holmes has just gotten out of prison for pickpocketing, and to keep him out of trouble, his brother, Mycroft (Max Irons), gets him a job at Oxford University as a scout. There, Holmes meets Moriarty, a brilliant student as smart as he is, and they quickly bond. Holmes’ time in Oxford takes a turn when he’s framed for the murder of a professor on campus, and so he and Moriarty set out to clear his name and find the real murderer. Their investigation takes them on a bigger journey in which they uncover some disturbing secrets of the Holmes family, as well as a deadly conspiracy. Now, while Young Sherlock makes some changes to canon, most notably the addition of a Holmes sister (Beatrice), it stays true to canon when it comes to Holmes and Watson’s first meeting. As such, Watson is not a part of Young Sherlock (for now, at least), so the show set Moriarty as Holmes’ sidekick. This pairing is interesting and exciting not just because it gives a backstory to Holmes and Moriarty and will explore how they ended up as enemies, but because Moriarty is known to be the only person whose intellect is at the level of Holmes’. This is a big part of the reason why Moriarty was Holmes’ archenemy, and watching him solve mysteries with someone who can easily keep up with him, his train of thought, add to it on the spot, and keep him on his toes is one of the best things about Young Sherlock. Young Sherlock Might Not Feature Watson At the time of writing, Young Sherlock will be coming back for a second season, which is expected to further explore Moriarty’s villainous turn after the first hints at it at the end of the first season. There’s still a lot more to learn and explore in Young Sherlock after the events of the first season, especially about Holmes’ family, which went through some massive shake-ups. On top of that is Holmes’ future as a detective, his friendship with Moriarty, and the latter’s plans behind Holmes’ back. In addition to all this, Watson doesn’t come into Holmes’ life until the latter is a well-established and known detective and they are both older, with Watson having served in the war. With this in mind, and while Young Sherlock has already made some changes to canon, it’s unlikely it will introduce Watson while he and Holmes are still young, and especially before Moriarty and Holmes’ friendship is over. It’s to be seen how far Young Sherlock will get and if that will allow it to introduce Watson at some point, but for now, it has an interesting dynamic by replacing him with Moriarty, through which it also answers the biggest questions about Holmes and Moriarty’s past. Release Date March 4, 2026 Network Prime Video Showrunner Matthew Parkhill Cast Hero Fiennes Tiffin Sherlock Holmes Zine Tseng Princess Gulun Shou’an