Looks like Claire Foy is turning in her crown for a hospital gown. 

The Crown star takes centerstage in the nerve-wracking new trailer, out Monday, for Unsane, a psychological thriller that focuses on Sawyer Valentini (Foy) who is involuntarily committed to a mental institution. 

As she tries to escape, she appears to slowly lose her mind, making it increasingly difficult to distinguish between reality and delusion. 

"I must be insane," Foy says in the clip, "Or maybe it's all in my head."

Directed by Steven Soderbergh (Ocean's Eleven), the film was shot on an iPhone

Juno Temple (Atonement), Aimee Mullins (Stranger Things), Amy Irving (Carrie), Joshua Leonard (The Blair Witch Project) and Jay Pharoah (Saturday Night Live) also star. 

Unsane hits theaters March 23.

Watch the full trailer below.