According to The Hollywood Reporter, Hamm joins Emily Browning, Vanessa Hudgens, Jamie Chung, Jena Malone, Abbie Cornish and Carla Gugino in the 1950s-set tale of a girl (Browning) confined to a mental institution by her stepfather, who intends to have her lobotomized in five days. She and her friends enter an alternate reality where they begin planning an escape.
Although details for Hamm's character are being kept under lock and key, the name is known: High Roller.
Snyder, who wrote the script, is producing with his Cruel & Unusual Films partner, wife Deborah Snyder.
The film begins shooting in early fall.