Our intrepid narrator, a former schoolteacher famously called Ishmael, signs up as sailor on a whaling voyage to cure a bout of depression. On his way to find a ship in Nantucket, he meets Queequeg, a heavily tattooed South Sea Island harpooneer just returned from his latest whaling trip. Ishmael and Queequeg become best buds and roommates almost immediately. Together, they sign up for a voyage on the Pequod, which is just about to start on a three-year expedition to hunt sperm whales.
On board the Pequod, Ishmael meets the mates − honest Starbuck, jolly Stubb, and fierce Flask − and the other harpooneers, Tashtego and Daggoo. The ship’s commander, Captain Ahab, remains secluded in his cabin and never shows himself to the crew. The mates organize the beginning of the voyage as though there were no captain.
Just when Ishmael’s curiosity about Ahab has reached a fever pitch, Ahab starts appearing on deck – and we find out that he’s missing one leg. When Starbuck asks if it was Moby Dick, the famous White Whale, that took off his leg, Ahab admits that it was and forces the entire crew to swear that they will help him hunt Moby Dick to the ends of the earth and take revenge for his injury. They all swear.
After this strange incident, things settle into a routine on board the good ship Pequod. While they’re always on the lookout for Moby Dick, the crew has a job to do: hunting sperm whales, butchering them, and harvesting the sperm oil that they store in huge barrels in the hold.
Ishmael takes advantage of this lull in plot advancement to give the reader lots of contemporary background information about whale biology, the whaling industry, and sea voyages. The Pequod encounters other ships, which tell them the latest news about the White Whale. Oh yeah, and everyone discovers that Ahab has secretly smuggled an extra boat crew on board (led by a mysterious, demonic harpooneer named Fedallah) to help Ahab do battle with Moby Dick once they do find him.
Over the course of more than a year, the ship travels across the Atlantic, around the southern tip of Africa, through the Indian Ocean, among the islands of southeast Asia, into the Sea of Japan, and finally to the equator in the Pacific Ocean – Moby Dick’s home turf.
Despite first mate Starbuck’s misgivings and a variety of bad omens (e.g., all the navigational instruments break, a typhoon tries to push the ship backwards, and the Pequod encounters other ships that have lost crewmembers to Moby Dick’s wrath), Ahab insists on continuing to pursue his single-minded revenge quest. In a parody of the Christian ceremony of baptism, he goes so far as to dip his specially forged harpoon in human blood– just so that he’ll have the perfect weapon with which to kill Moby Dick.
Finally, just when we think the novel’s going to end without ever seeing this famous White Whale, Ahab sights him and the chase is on. For three days, Ahab pursues Moby Dick, sending whaling boat after whaling boat after him – only to see each one wrecked by the indomitable whale. Finally, at the end of the third day, the White Whale attacks the ship itself, and the Pequod goes down with all hands.
Even while his ship is sinking, Ahab, in his whaling boat, throws his harpoon at Moby Dick one last time. He misses, catching himself around the neck with the rope and causing his own drowning/strangling death.
The only survivor of the destruction is Ishmael, who lives to tell the tale because he’s clinging to the coffin built for his pal Queequeg when the harpooneer seemed likely to die of a fever.