Linda Cardellini (Crystal Lake) is starring in They Know.

Bill Hader writes, directs and stars in the upcoming horror movie, based on an original story Hader created with Barry collaborator Duffy Boudreau.

They Know centers on a divorced dad (Bill Hader) who grows suspicious that his ex-wife is secretly dating a mysterious man who is having a strange influence on their children.

MRC is the studio financing the feature film.

Bob Graf and Bill Hader will produce via Hanarply, with Alyssa Donovan co-producing.

Deadline first reported on Cardellini’s casting.