Theron stars as Marlo, a mother of three (including a frequently-crying newborn) who struggles before her brother hires her a night nanny. Mackenzie Davis (Halt and Catch Fire, Blade Runner 2049) plays Tully, the “thoughtful, surprising, and sometimes challenging young nanny” with whom Theron’s character forms a “unique bond,” according to the film’s official synopsis.

Of taking on the role, Theron recently told PEOPLE, “I don’t think I could’ve done this film without having experienced motherhood yet, so this film came at the perfect time for me. There’s so much pressure on parents to balance everything in their life so perfectly and to do it with a smile. So I wanted to tell a story that shows parents, ‘Hey, life is a lot harder for us, and it’s okay if you have to get help.’”

The film — which reunites Theron with her Young Adult screenwriter Diablo Cody and director Jason Reitman — also stars Mark Duplass as Marlo’s brother and Ron Livingston (Search Party, Boardwalk Empire) as her husband.