Families can be monstrous and their secrets dangerous, as New Scotland Yard detectives Thomas Lynley and Barbara Havers have discovered. The pair are puzzled that the Hampstead police need their help investigating the vehicular murder of a middle-aged divorcée, until they find evidence that one of their own superiors once knew the dead lady very well indeed. But the circumstances of Eugenie Davies's murder appear to center on her children: Gideon, a famous violinist now undergoing psychoanalysis for his sudden inability to play, and the long-dead Sonia, a disabled baby whose drowning death was shrouded in secrecy for her virtuoso brother's sake--at the insistence of their father, Richard--but also trumpeted in the press as the infamous "nanny murder" of its day. The nanny, Katja Wolff, has recently been released from prison, having never spoken of the night Sonia drowned. Lynley, Havers, and their colleague Winston Nkata know that whatever secret Katja Wolff has been hiding must be the cause of Eugenie Davies's death, but before they can find out what it is, another deliberate hit-and-run occurs in their own backyard.