What was supposed to be a routine mission becomes an unprecedented disaster for the whaleship Essex.
Launched from Nantucket in 1819, the Essex is expected to take a two- to three-year jaunt to the Pacific Ocean before returning home with oodles of whale oil. Led by the newly promoted Captain George Pollard Jr. and his mates Owen Chase and Matthew Joy, the Essex is manned by an amateurish crew that includes fourteen-year-old Thomas Nickerson and Chase's nephew Owen Coffin.
Within a few days, the Essex nearly flips after being slammed by a freak storm. Though Captain Pollard wants to return to Nantucket for repairs, he's convinced to continue by Chase and Joy. Unfortunately, they have a tough time finding whales—they don't spot a single one until crossing the equator. Thankfully, their luck turns around by the time they round the base of South America.
After reaching the Pacific Ocean, the crew decides to head to the Offshore Grounds, a newly discovered breeding ground that boasts tons of whales but is thousands of miles away from land. During a hunt, the Essex is shockingly attacked by a sperm whale—the first recorded instance of an intentional attack on humans by a sperm whale. Chase misses an opportunity to kill the whale before this happens, which is a failure that haunts him for the rest of his life.
Desperate, the surviving crewmembers rig their tiny whaleboats with sails and attempt to make the long journey to South America. Each officer is placed in charge of a whaleboat: Coffin is on Uncle Pollard's crew, while Nickerson travels with Chase. Once again, Pollard has only been convinced of this (risky) course of action thanks to the prodding of Chase and Joy: he had wanted to travel to the Society Islands instead. Oh, if only he had insisted.
Although they hit a few strokes of luck—catching a few fish and chancing upon a tiny island, for example—the whaleboats are eventually separated, and the starving sailors descend into (oops) cannibalism. At one point, Pollard's crew runs out of food, and Owen Coffin is killed and eaten. In the end, five sailors (including Pollard, Chase, and Nickerson) are rescued near the coast of South America (three men had remained on that tiny island and were rescued later), though the Essex tragedy continues to haunt them until their deaths.