Prime Video’s Young Sherlock series is adding another big name to its cast.

Colin Firth has joined the Guy Ritchie-directed show, which is inspired by author Andy Lane’s Young Sherlock Holmes novel series. Firth joins a cast that also includes Hero Fiennes Tiffin in the title role, Joseph Fiennes and Natascha McElhone as Sherlock’s parents and Zine Tseng as Princess Gulun Shou’an.

Firth will play a character named Sir Bucephalus Hodge; details on the role are being kept quiet for now.

Young Sherlock is described as a reimagining of the iconic detective, in the spirit of Ritchie’s two Sherlock Holmes feature films. The series follows Sherlock as a 19-year-old who is “disgraced, raw, unfiltered, and unformed, when he finds himself caught up in a murder mystery at Oxford University which threatens his freedom. Diving into his first-ever case with a wild lack of discipline, Sherlock manages to unravel a globe-trotting conspiracy that will change his life forever.”

Matthew Parkhill (Rogue) is adapting Lane’s novels and will serve as showrunner on the series. Parkhill and Ritchie executive produce with Simon Kelton, Ivan Atkinson, Simon Maxwell, Dhana Gilbert, Colin Wilson and Marc Resteghini. Harriet Creelman is co-EP.

The series will be Firth’s second for a U.S.-based streamer, following 2022’s The Staircase at Max (for which he earned an Emmy nomination). Other recent credits include the Kingsman films, Sam Mendes’ Empire of Light and 1917 and Netflix’s Operation Mincemeat. He is repped by CAA, Independent Talent in the U.K. and Prosper PR.