In "The Colomber," a boy named Stefano Roi accompanies his father, who is a sea captain, aboard his boat and sees a strange fish on the horizon. His father explains that Stefano has seen a colomber, a kind of shark who follows his victim without ceasing and who can only be seen by the intended victim and his or her family. The father believes that the colomber will devour Stefano, so he sends his son away to an inland school. Eventually, Stefano takes up work in a store, but he feels drawn to the sea. After his father dies, Stefano, consumed by thoughts of the colomber (who he continues to see from the dock), becomes a successful sailor. His desire to escape the colomber makes him an able and determined sailor.

When Stefano is old, he realizes that the colomber has pursued him for 50 years. He decides to meet the fish, and he takes a small boat out to where the fish lurks in the water. In a strange way, he admires the fish's fidelity to him. When Stefano meets the fish, the fish gives him a magnificent pearl, called the Perla del Mare, which confers power and good luck on those who have it. The fish explains that he never meant to harm Stefano, and then the fish disappears forever. Stefano realizes too late that he has destroyed his own life (and that of the colomber) by fearing the fish. Two months later, fishermen find Stefano's skeleton grasping a small stone.