A Traitor to Memory (Inspector Lynley #11) by Elizabeth George

Twenty-eight-year old virtuoso violinist Gideon Davies has lost his memory of music and his ability to play the instrument he mastered as a five-year-old prodigy. One fateful night he lifted his violin to play in a Beethoven trio . . . and everything in his mind related to music was gone. Gideon suffers from a form of amnesia, the cure for which is an examination of what he can remember. And what he can remember is little enough until his mind is triggered by the weeping of a woman and a single name: Sonia.

Then, one rainy evening, Gideon’s mother Eugenie travels to London for a mysterious appointment. But before she is able to reach her destination, a car swoops out of nowhere and kills her in the street.In pursuing Eugenie’s killer, Lynley and Havers come to know a group of people whose lives are inextricably connected by a long-ago death, a trial, and a prison sentence handed down as retribution for a crime no one has spoken of for twenty years.