Lincoln Rhyme and Amelia Sachs take on the investigation of a brutal triple murder in Manhattan's Diamond District. The killer, known as the Promisor, is murdering men and women midway through the purchase of an engagement ring. In the early hours of a quiet, weekend morning in Manhattan's Diamond District, at the scene of a brutal triple murder, the killer left behind a half-million dollars' worth of gems at the scene. As more crimes follow, it becomes clear that the killer's target is not gems, but engaged couples themselves. Then a witness is left alive. Vimal Lahori, a young diamond cutter, can help Rhyme and Sachs blow the lid off the case-- but has gone into hiding. They must track down Vimal before the killer can correct his fatal error.

Sequel to: The burial hour.