MI5 security officer Eve Polastri is bored in her job and yearns for a more exciting life. When a Russian politician is murdered, Eve is tasked with protecting the only witness and soon finds herself on a collision course with violent and extraordinary assassin, Villanelle.

When Villanelle kills a Chinese Colonel at a kink clinic in Berlin, Eve and Bill travel out to investigate. While Eve and Bill chase up a number of promising leads, Villanelle enjoys the cat and mouse of their proximity. But as they draw closer, Eve comes to realise that this is much more than a game.