Pilot season brings us news of another network taking on a Marvel Entertainment property: FX is developing the pilot for Legion, about a man named David Haller, troubled by voices in his head… and also (in the Marvel Comics, at least) the mutant son of Professor Charles Xavier. While the network ordered the pilot a few months ago, casting news announced today brings the project closer to a greenlight. Downton Abbey‘s Dan Stevens and the wonderful Aubrey Plaza have signed on to play the two leads.

First, some more about the show:

Since he was a teenager, David has struggled with mental illness. Diagnosed as schizophrenic, David has been in and out of psychiatric hospitals for years. But after a strange encounter with a fellow patient, he’s confronted with the possibility that the voices he hears and the visions he sees might be real.

First appearing in New Mutants #25 in 1985, David Charles Haller, a.k.a. Legion, has become something of an antihero, struggling with dissociative identity disorder in which his alternate personalities each control a different power. It will be interesting to see how much FX will pull from his story in the comics for their pilot. Fargo‘s Noah Hawley is set to write and executive produce, alongside Lauren Shuler Donner (X-Men: Days of Future Past, The Wolverine), Bryan Singer (X-Men: Days of Future Past, Superman Returns), Simon Kinberg (X-Men: Days of Future Past, The Martian), Jeph Loeb (Agents of S.H.I.E.L.D., Daredevil), Jim Chory (Agents of S.H.I.E.L.D., Daredevil), and John Cameron (Fargo, The Big Lebowski).

Today’s announcement included a character breakdown:

DAVID (Dan Stevens) – Diagnosed as schizophrenic at a young age, David 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. LENNY (Aubrey Plaza) – David’s friend, who despite a life of drugs and alcohol abuse, knows that any day now her life is gonna turn around, which gives Lenny the likeable energy of the impossible optimist despite her rough demeanor. MELANIE (Jean Smart) – A nurturing, demanding therapist with a sharp mind and unconventional methods. SYD (Rachel Keller) – 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.

We love Plaza in most things—and she was especially fantastic in the time travel indie Safety Not Guaranteed—but here’s hoping her role as Lenny isn’t just in service to David’s character development. Legion begins production in March.