For a major new comic book property, FX’s X-Men TV series Legion has been curiously silent in recent weeks, following its first casting, and a few TCA updates. Now, showrunner Noah Hawley drops a huge X-bomb, as Dan Stevens, Aubrey Plaza and another Fargo alum have been tapped for the lead roles of Professor Xavier’s child David Haller, and support cast.

Downton Abbey alum Stevens will play David as a haunted man, trying to find his way back to sanity, but tired and about to give up until he meets the girl of his dreams. Plaza, meanwhile, will play David’s alcoholic, drug-abusing friend Lenny, who “knows that any day now her life is going to turn around — which gives Lenny the likeable energy of the impossible optimist despite her rough demeanor.”

Fargo alum Jean Smart will play Melanie, “a nurturing, demanding therapist with a sharp mind and unconventional methods,” joining fellow Hawley favorite Rachel Keller as “Syd,” described as “Self-sufficient and street smart.” Syd uses her sharp and prickly demeanor to protect her soft core, because even though it makes her a sucker and puts her at risk, she still believes in happily ever after.

For those unaware, Legion follows the story of David Haller, a young mutant struggling with schizophrenia and psychiatric incarceration, who soon learns from a fellow patient that his voices and visions may in fact be real. Created for the New Mutants in 1985, the character is also noted as the son of Professor Charles Xavier and Gabrielle Haller.

FX also specified the series was likely to feature all-new characters from the X-Men universe, independent of the movies’ continuity. Additionally, Fargo showrunner Hawley will write the pilot and serve as an executive producer alongside Lauren Shuler Donner, Bryan Singer, Simon Kinberg and Marvel’s Jeph Loeb.

We’ll keep up to speed on the latest details, but what do we make of Stevens, Plaza and Smart joining Legion for the new X-property?

Check Out 100 Movie Facts You May Not Know