Celia Ashton has driven ambulances throughout the Blitz for the Bloomsbury Auxiliary Ambulance Depot. Cool under fire, she revels in her exciting and extremely dangerous job. When her husband, a known Nazi supporter, is released from prison, Celia refuses to return to her unhappy marriage. Instead she joins forces with Simon Levy, a man who appears to despise her, to help a young Jewish orphan. In so doing she discovers that one ruthless traitor can be more dangerous than any German bomber, and that love can cross any boundary.