Eve (Sandra Oh) is a low-level MI5 security officer stuck in a mundane desk job, far from her secret desire to be a spy. Meanwhile, Villanelle (Jodie Comer) is a dangerous, capricious assassin who enjoys the luxuries that come with her violent profession. When Eve connects a series of murders across Europe to Villanelle, she is hired to track the killer. The two become obsessed with each other, entering into an epic and perilous game of cat and mouse.