<div>Commissario Brunetti and his assistant Vianello secure the release of Marco Ribetti, arrested during an environmental protest, only to face the fury of the man's father-in-law, Giovanni De Cal, a cantankerous glass factory owner who has been heard in the bars of Murano making violent threats against Ribetti. Brunetti's curiosity is piqued, and he beings to investigate: Is De Cal the type of man to carry out his threats? By all accounts he is constantly angry, bullying suppliers and fuming against environmentalists. Then one morning the body of De Cal's bookish night watchman is found in front of the blazing furnace. Could the old man have done it? And who is posioning the waters of Venice's lagoon? Fighting against time, Brunetti must find the murderer before he strikes again.</div>