When two young American women are badly injured in a boating accident, Commissario Brunetti's eye turns to the two young Italians they were with, who abandoned them in the hospital. When one of the young men is found to be involved in more sinister night-time activities in the Laguna, Brunetti has to enlist the help of Italian institutions to get to the bottom of the mystery.

But can Brunetti trust unfamiliar colleagues? Could there be another motive behind this horrible crime?