White-jacket is a sailor on the U.S. frigate Neversink. His nickname derives from a jacket stitched together from leftover scraps of rags. This jacket makes the other sailors superstitious and as the ship heads towards Antarctica his mess group kicks him out and he joins another group, serving under the much-liked petty officer, Jack Chase.

The journey is a dangerous one. A man falls overboard. There are constant floggings for the merest inkling of insurrection. All the crew members are forced to watch each flogging. A doctor stands by to stop the flogging if the victim's life is endangered, but he is so callous he doesn't stop a single one. The doctor also prescribes medications, but never attempts to change the conditions that cause the sailors' illnesses, like malnutrition and exposure.

When the ship lands in Rio de Janeiro, Dr. Cadwaller Cuticle boards. In order to show off to the ship's doctors, he amputates the healthy leg of a sailor, who is terribly frightened as the doctors discuss his impending fate in front of him. The man dies of shock. When the boat continues on its journey, White-jacket accidentally falls from the riggings. He barely escapes being speared when a ship-mate mistakes his jacket for a whale. He is fished out and sent up again to complete his task.