Watson Season 2 cast and character guide: Every returning star and new appearance confirmed so far

Watson Season 2 picks up right where the CBS medical mystery drama left off, but with a major twist, Sherlock Holmes is alive. After an entire season built on the belief that Holmes died at the hands of Moriarty, the new season throws the assumption out the window, and forces John Watson to face not only his former best friend but a dangerous truth hidden in his own body.

Robert Carlyle joins the show as Holmes in a recurring role, while Morris Chestnut returns as Dr. John Watson, who continues running his Holmes Clinic in Pittsburgh, solving rare medical mysteries alongside a team of brilliant but complicated specialists.

The season is expected to deepen the emotional and medical stakes. Watson’s head injury from the Moriarty incident continues to affect him. Meanwhile, Moriarty’s shadow still looms large, and Holmes’ reappearance might be more of a curse than a blessing.

Alongside returning cast members like Rochelle Aytes, Eve Harlow, and Peter Mark Kendall, new additions include Ritchie Coster, Inga Schlingmann, and of course, Carlyle as the not-so-dead detective. With secrets from the past crashing into the present, Watson Season 2 brings together a cast built for drama and complex mystery-solving.

Every confirmed cast member in Watson Season 2

Watson Season 2 brings back the core team and adds some big names that shift the dynamic in major ways. Morris Chestnut returns as Dr. John Watson, still haunted by the trauma of Sherlock’s supposed death and his own brain injury.

He continues to run the Holmes Clinic, where his patients often present rare, hard-to-diagnose conditions. Chestnut, already known for The Resident and Nurse Jackie, keeps the focus on Watson’s emotional and physical recovery, while still making him a steady presence in the show.

Rochelle Aytes is back as Dr. Mary Morstan, Watson’s ex-wife. Their relationship remains complicated, but Mary plays an essential role in keeping the clinic grounded. She is practical, focused on outcomes, and doesn’t let Watson spiral too far into personal theories or past regrets.

Eve Harlow returns as Ingrid Derian, the neurologist with unconventional methods and an offbeat personality. Her character adds scientific insight and occasional tension to the team’s problem-solving process.

Peter Mark Kendall continues in his dual role as twin brothers Dr. Adam and Dr. Stephens Croft. One is charming, the other stoic, but both are experts in infectious disease. Their back-and-forth dynamic serves as both comic relief and scientific backup, especially when cases push the limits of medical logic.

Inga Schlingmann plays Sasha Lubbock, the clinic’s immunology specialist. Her story adds cultural depth as she navigates her identity between two very different families, her Chinese birth parents and her Christian adoptive ones.

New to Season 2 is Robert Carlyle, who plays Sherlock Holmes in a recurring guest role. His return adds a completely new layer to the show, especially since Watson believed Holmes was dead.

The reveal doesn’t just raise questions, it forces Watson to re-evaluate years of trust and unresolved trauma. Carlyle, known for Trainspotting and Once Upon a Time, brings a version of Holmes who’s enigmatic, worn, and possibly hiding more than he’s letting on.

Ritchie Coster joins as Shinwell Johnson, a reformed criminal working as an administrative aide at the Holmes Clinic. He’s not just a background character. Shinwell’s connections in Pittsburgh’s underworld are crucial to cases that require information outside legal channels. Coster’s known for playing morally ambiguous characters, and here too, Shinwell operates in that gray area.

Also returning are Randall Park as Moriarty, Adrian Holmes as Detective Marcus Hayes, and Fiona Vroom as Dr. Lily Park. Park’s Moriarty may not appear in every episode, but his presence continues to shape Watson’s paranoia. Holmes’ detective still works cases with Watson, while Vroom's Lily Park returns as a surgical consultant called in for complex cases.

With this complete mix of returning stars and new additions, Watson Season 2 has all the pieces in place for more complicated mysteries and deeper character stories - without sidelining any of the original cast.

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