When two young American women are badly injured in a boating accident, joy riding in Venice's Laguna with two young Italians, Commissario Guido Brunetti's curiosity is aroused by the behaviour of the young men, who abandoned the victims after taking them to the hospital.
As Brunetti and his colleague, Claudia Griffoni, investigate, they discover that one of the young men works for a man rumoured to be involved in more sinister night-time activities...