Dan Stevens has been cast as the lead protagonist, David Haller, in FX’s upcoming X-Men spinoff pilot Legion.

Stevens (Downtown Abbey) will be joined by Aubrey Plaza (Parks and Recreation) and Jean Smart (Fargo) in supporting roles.

Legion is based on the X-Men character of the same name, the mutant son of Professor Charles Xavier, a.k.a. Professor X. In addition to being a powerful mutant, Haller is a diagnosed schizophrenic. Each of his different personalities controls a different mutant gift.

According to announcement, Stevens’ Haller is “a haunted man, trying to find his way back to sanity, but he's getting tired and is about to give up when he meets the girl of his dreams.” The announcement offered no further details on David's dream girl, but fans of the character's latest stories in the pages of X-Men: Legacy will know that he fell for the young mutant precognitive called Blindfold.