FX has brought in some pretty big names for their X-Men show Legion. According to The Hollywood Reporter, they have tapped Downton Abbey’s Dan Stevens, Parks and Recreation’s Aubrey Plaza, and Fargo’s Jean Smart to star in the pilot episode.

Legion is a joint production from FX Productions and Marvel Television with FX Productions overseeing the production. The story will be written by Noah Hawley (Fargo) who will also serve as an executive producer alongside Lauren Shuler Donner, Bryan Singer, Simon Kinberg, Jeph Loeb, Jim Chory, and John Cameron.

The story will center around David Haller, a man who has struggled with mental illness. He is a diagnosed schizophrenic and has been in and out of psychiatric hospitals for years. However, he is confronted with the idea that the voices and visions he encounters may actually be real. In the comics, David Haller was the son of X-Men founder and super psychic Charles Xavier. He first appeared in New Mutants #25.

Dan Stevens will portray the mentally ill Haller who is is on the precipice of giving up until he meets the girl of his dreams. Aubrey Plaza will portray Lenny, David’s best friend who has her own troubles with addiction including drugs and alcohol. However, she will be an impossible optimist believing any day her life will turn around.

Finally, Jean Smart is set to portray Melanie a nurturing and demanding therapist who uses some unconventional methods to achieve results.

All three will join previously announced, Rachel Keller, who has been cast as the female lead, Syd. Syd is self-sufficient with a prickly personality. Much like Lenny she is still optimistic believing in her happily ever after.

Production for the show is expected to begin this March.