Rose (Emily Blunt) is a beautiful, quick-witted con-artist, who makes a killing selling fake paintings. But when she scams an art loving gangster (Rupert Everett) he sets Europe's most efficient and expensive assassin on her tail.
Enter Victor Maynard (Bill Nighy). He sets out on the assignment with his usual lethal professionalism. Yet every time Victor has Rose in his sights something holds him back. Entranced by the spirited Rose, Victor spares her life and becomes her protector, accidentally acquiring a young apprentice (Rupert Grint) into the bargain.
Now on the run, Victor has to fight both his feelings for Rose and the murderous attentions of the second most expensive' assassin (Martin Freeman), sent to finish off all three of them.