Yvonne Carmichael is a geneticist, a scientist renowned in her field but one day, she makes the most irrational of decisions. While she is giving evidence to a Select Committee at the Houses of Parliament, she meets a man and has sex with him in the secluded Chapel in the Crypt beneath the Great Hall of Westminster. It's the beginning of a reckless liaison, but there is more to her lover than is at first apparent - as Yvonne discovers when the affair spins out of control and leads inexorably to violence.