There are two types of people in the world: those who can only remember yesterday, and those who can also recall the day before. You have just one lifeline to the past: your diary. Each night, you write down the things that matter. Each morning, your diary tells you where you were, who you loved and what you did. Today, the police are at your door. They say that the body of your husband's mistress has been found in the River Cam. They think your husband killed her two days ago.