EXCLUSIVE: Masters Of Sex star Lizzy Caplan is joining the cast of the untitled film that Robert Zemeckis will direct with Brad Pitt and Marion Cotillard from a script by Steven Knight. The film is backed by Paramount Pictures, GK Films and New Regency.

The title and plot are shrouded in secrecy, but I’ve heard that Caplan will play Pitt’s character’s sister.

GK Films’ Graham King is producing the film with ImageMovers’ Zemeckis and Steve Starkey, with Jack Rapke, Knight, Patrick McCormick and Denis O’Sullivan exec producing.

Caplan has Now You See Me 2 coming out in June and this summer she begins production on Season 4 of Showtime’s Masters Of Sex. She is repped at WME, Rise Management and Jackoway Tyerman.