During the year 1866, ships of various nationalities sight a mysterious sea monster, which, it is later suggested, might be a gigantic narwhal. The U.S. government assembles an expedition in New York City to find and destroy the monster. Professor Pierre Aronnax, a French marine biologist and the story's narrator, is in town at the time and receives a last-minute invitation to join the expedition; he accepts. Canadian whaler and master harpooner Ned Land and Aronnax's faithful manservant Conseil are also among the participants.