Detectives Nic Costa and Gianni Peroni are nearing the end of their exile in Venice following a little bit of insubordination on a case in Rome. Their girlfriends are arriving shortly to join them for a holiday before they all return to Rome. When they're ordered to investigate two deaths which occurred at the same time as a fire in a glass foundry in the island of Murano they're not exactly enthusiastic particularly when it seems that they're being railroaded into writing the deaths off as accidental.