'Listen: I'm not a bad person. I'm a doctor. One of the reasons I wanted to become a doctor was because I thought it would be a good - as in Good, rather than exciting or well-paid or glamorous - thing to do...Anyway. I'm a good person, a doctor, and I'm lying in a hotel bed with a man I don't really know very well called Stephen, and I've just asked my husband for a divorce.' According to her own complex moral calculations, Katie Carr has earned her affair. She's a doctor, after all, and doctors are decent people, and on top of that her husband David is the self-styled Angriest Man in Holloway. When David suddenly becomes good, however - properly, maddeningly, give-away-all-his-money good - Katie's sums no longer add up, and she is forced to ask herself some very hard questions.