Commissario Brunetti faces a heinous crime committed outside his jurisdiction: two young American women have been badly injured in a boating accident, joy riding in the Laguna with two young Italians. As Brunetti and his colleague, Claudia Griffoni, investigate the incident, they discover that one of the young men works for a man rumoured to be involved in more sinister night-time activities in the Laguna. To get to the bottom of what proves to be a gut-wrenching case, Brunetti needs to enlist the help of both the Carabinieri and the Guardia di Costiera. The presence of these unfamiliar colleagues adds to the difficulty of solving a peculiarly horrible crime whose perpetrators are technologically brilliant and ruthlessly organized.