Commissario Brunetti is investigating a cold case by request of the grand Contessa Lando-Continui. 15 years ago her teenage granddaughter, Manuela, was found drowning in a canal. She was rescued at the last moment but in many ways it was too late; she suffered severe brain damage and life was never the same again. Once a passionate horse rider, Manuela, now aged 30, cannot remember the accident, or her beloved horse, and lives trapped in an eternal youth. The Contessa, unconvinced that this was an accident, implores Brunetti to find the culprit she believes was responsible for ruining Manuela's life. Out of a mixture of curiosity, pity, and a willingness to fulfil the wishes of a loving grandmother, Brunetti reopens the case, much to the annoyance of his employer. But once he starts to investigate, he finds a murky past with a dark story at its heart.