Yvonne Carmichael, renowned geneticist, public authority, happily married mother of two, sits in the accused box. The charge is murder. Across the courtroom, not meeting her eye, sits her alleged accomplice. He wears the beautiful pin-striped suit he wore on their first meeting in the Houses of Parliament, when he put his hand on her elbow, guided her to a deserted and ancient chapel, and began to undress her. As the barrister's voice grows low and sinuous, Yvonne realizes she's lost herself and the life she'd built so carefully to a man who never existed at all.
After their first liaison, Yvonne's lover tells her very little about himself, but she comes to suspect his secrecy has an explanation connected with the British government. So thrilled and absorbed is she in her newfound sexual power that she fails to notice the real danger about to blindside her from a seemingly innocuous angle. Then, reeling from an act of violence, Yvonne discovers that her desire for justice and revenge has already been compromised. Everything hinges on one night in a dark little alley called Apple Tree Yard.