Everyone said Cassie (Carey Mulligan) was a promising young woman ... until a mysterious event abruptly derailed her future. But nothing in Cassie’s life is what it appears to be: she’s wickedly smart, tantalizingly cunning, and she’s living a secret double life by night.
Now, an unexpected encounter is about to give Cassie a chance to right the wrongs of the past in this thrilling and wildly entertaining story.

The film won the Best Original Screenplay at the 93rd Academy Awards. Fennell also won Best Original Screenplay at the Critics' Choice Awards, Writers' Guild Awards and British Academy Film Awards.