Ishmael arrives in New Bedford in winter, meets Queequeg at the Spouter-Inn, and the two form an unlikely friendship before signing aboard the Pequod. Ahab remains absent. Ominous warnings from Elijah are brushed aside.

Ahab finally appears on deck — scarred, ivory-legged, terrifying. He nails a gold doubloon to the mast and reveals his true purpose: finding and killing Moby Dick. The crew is swept into his obsession; Starbuck resists but fails to stop him.

Melville interrupts the narrative repeatedly to deliver encyclopedic lectures on whale biology, whale taxonomy, the technology of whaling, and the history of how human cultures have tried — and failed — to understand the whale. These chapters ARE the novel's argument.

The Pequod meets a series of other ships at sea. Each 'gam' — a meeting between ships — brings news of Moby Dick and forces Ahab to choose between human connection and his obsession. Ahab almost always chooses obsession. The Samuel Enderby's captain, who also lost a limb to Moby Dick, chose differently.

Melville introduces his extraordinary crew — Starbuck, Stubb, Flask, Queequeg, Tashtego, Daggoo, Pip — and explores what it means for a democratic crew to be conscripted into one man's private war. Each crewman represents a different response to Ahab's authority.

As the voyage deepens, Ahab's symbolic acts multiply: he throws his pipe overboard, destroys the quadrant with his foot, makes a new compass needle by magnetizing a needle in a storm. He is systematically destroying the instruments of rational navigation. Queequeg orders a coffin built, then recovers, and it becomes a life-buoy.

Fedallah, the mysterious Parsee harpooner Ahab secretly brought aboard, serves as Ahab's dark prophet. His prophecies seem to promise Ahab immortality — but are structured as riddles that will prove literally true in devastating, unforeseen ways.

Moby Dick is sighted. The three-day chase is among the most sustained action sequences in American literature. Each day escalates: boats smashed, lines cut, men killed. On the third day, Moby Dick destroys the Pequod, and the harpoon line drags Ahab into the sea. All hands are lost.

Ishmael, the sole survivor, explains how he lived: floating on Queequeg's coffin, picked up by the Rachel. The Job epigraph — 'And I only am escaped alone to tell thee' — frames the entire novel as a survivor's testimony before a God who may not be listening.