Through a Glass, Darkly - S1.E15

The Venetian island of Murano is known for its artisans who specialize in the traditional craft of glassmaking. When the owner of a glass factory is found murdered, Commissario Brunetti uncovers a connection between the colorful, filigree glass products that he made and some very toxic poisons. How else to explain the colorful slime containing arsenic oozing out from the factory?