“Downton Abbey” fans will see Dan Stevens return to television soon, but he won’t be playing Matthew Crawley again. The British actor will star in FX’s new X-Men show, titled “Legion.”

Stevens will play David Haller, the son of Charles Xavier, TVLine reports. However, he hasn’t spent much time with is father. He’s been in a series of mental institutions for most of his life while being treated for schizophrenia. He meets a fellow patient who convinces him that his visions are real.

Aubrey Plaza stars as his drug addict friend, Lenny, and Jean Smart plays a therapist. Rachel Keller was previously announced as a cast member, but few details were released about the character. “Fargo” creator Noah Hawley serves as executive producer for the show, which is based on Marvel’s “Legion” comics. Hawley seemed excited to reveal the casting news Thursday.

When FX announced the drama in October, the showrunner noted that David isn’t simply a misdiagnosed mutant. “What I really like about him is, here's a character who is schizophrenic on some level, a character struggling with mental illness,” Hawley told TV Insider. “Is he crazy or does he have these powers? The answer is, kind of both. I'm a big believer that the structure of a story should reflect the content of the story. And so I liked the idea that if you have a character that doesn't know what's real and what's not real, that is also the audience's journey.”

The FX drama will be Stevens’ first role as a series regular since leaving “Downton Abbey” in 2012. He spent three years on PBS’ British import before his beloved character was killed off. He has added several roles to his resume since then, including “Night at the Museum: Secret of the Tomb” and the highly anticipated live action “Beauty and the Beast,” which is scheduled to come out in 2017.

“Legion” does not yet have a premiere date. The cast will start filming next month.