Zoë Boehm doesn't do death. It's a rule. Yet here she is—in this new ambitious detective novel from the sure-footed Mick Herron—worried by three of them. Zoë herself has killed a man, and self-defense or not, it cripples her emotions still. She also remembers Wez, a twelve-year-old kid afraid of heights, who tumbled to his death from the top of a tower block; she knew him when he was nine and snatching purses from middle-aged ladies. Then, there's Caroline Daniels. They're saying that Caroline's death was accidental: that she fell off the crowded underground platform and died beneath the wheels of an oncoming train. Nonetheless, Caroline's employer, Amory Grayling, is disturbed. Caroline, it seems, had recently acquired a lover who remains mysteriously faceless and nameless. So it is that Zoë begins searching for a man whom no one knows by attempting to uncover the secrets locked in the heart of a woman she has never met. Though the questions outnumber Zoë's answers, she is certain that Caroline did not fall accidentally to death. Nor did Wez, she comes to realize, and soon finds herself dangerously pursuing two murderers, though one of them may find her first.