Guy Ritchie's Sherlock Prequel Series Has Fully Replaced Watson

Published Aug 11, 2026, 7:31 PM EDT

In recent years alone, CBS’s Watson reimagined Sherlock’s partner Dr. Watson as the head doctor at a trauma clinic, returning to work after Sherlock’s death, while the Enola Holmes movies were a set of fun romps that focused on Sherlock’s free-spirited little sister, played by Millie Bobby Brown. Even the British gangster movie legend Guy Ritchie has gotten in on the action in 2026, parlaying the success of his two Sherlock Holmes movies with a prequel show on Prime Video.

Although Young Sherlock technically centers on the title character’s early years as an amateur sleuth while attending Oxford University, Hero Fiennes Tiffin’s titular antihero isn’t the only lead character who wowed reviewers upon the release of the show’s first outing. Dónal Finn’s Moriarty is Sherlock’s unlikely partner in investigation and, despite a strong supporting cast that includes Joseph Fiennes, Natascha McElhone, Colin Firth, and Numan Acar, it is the pair’s work together that makes the series a must-watch.

It's Fascinating To See Someone Else Partnering With Sherlock

By now, viewers are used to attempts to reinvent the Holmes and Watson dynamic onscreen. There was John C. Reilly and Will Ferrell’s roundly reviled 2018 slapstick comedy Holmes & Watson, the aforementioned recent CBS medical drama Watson, BBC’s contemporary crime drama Sherlock, and Ritchie’s own Sherlock Holmes movies, 2009’s Sherlock Holmes and 2011’s Sherlock Holmes: A Game of Shadows.

While Jude Law’s Watson threatened to outshine Robert Downey Jr.’s Sherlock in those well-liked movies, it remains an incontestable reality that the Holmes/Watson dyad is hardly the most compelling element of any Sherlock Holmes adaptation. Even the savviest version of Watson and the silliest version of Holmes are ultimately bound to their original characterizations, wherein the relatable everyman Watson is stunned by the ingenious super detective’s powers of deduction every time.

Thus, it is inherently subversive to give the sidekick role instead to Moriarty in Ritchie’s Young Sherlock, since this reveals that the pair were friends before they became mortal enemies by the time Conan Doyle’s novels take place in the canon. It also makes Sherlock’s deductions and his sidekick’s reactions to them far more impactful, since Moriarty is unknowingly increasing his own understanding of his future foe by watching how Holmes solves mysteries.

It's Official: John Watson Is Just Sherlock Holmes' Replacement For Moriarty

The choice to pair up a younger version of Sherlock with Moriarty as his Watson stand-in is the sort of brilliant twist that feels obvious in retrospect. After all, this twist explains how Moriarty got under the skin of his nemesis, since Finn and Fiennes’ characters are inseparable in the Prime Video series.

It also explains why both of them think alike, which is how both Holmes and Moriarty manage to ensnare each other in inspired traps throughout the books in the series. Even though Ritchie’s Young Sherlock might be one of the first major adaptations to take this route, this twist makes so much sense that it now feels like it could become part of the fandom’s canon.

Moriarty being Holmes' original Watson before Watson was Watson explains so much about the pair’s later dynamic that it feels fated, and Prime Video’s show can now explore how the pair eventually became sworn enemies as the show’s story continues in future outings. Thus, Guy Ritchie’s Sherlock prequel Young Sherlock has successfully reinvented a story that seemed to be played out before the prequel came along.