When a ship pulls into port in Tahiti one day with a crew infected with smallpox, it desperately needs a new captain. No one is willing to accept the post, though, except for a washed-up former American ship's captain, Davis. He brings his two fellow homeless people along with him: Herrick, an unsuccessful businessman from England, and Huish, a Cockney crook and renaissance man. Unable to accept honest work, the three plan to take the ship to Peru and sell it and all its cargo then disappear and restart their lives there. The ship is chartered for Sydney. On the way, Davis and Huish remain continually drunk on the ship's cargo of champagne, forcing Herrick to try and command the ship on his own, with no experience.
During the voyage, they all discover that only half the cargo is champagne; the rest is water. Apparently, the previous captain, who died of smallpox, had intended on sinking the ship and collecting insurance upon the full cargo. This is an unfortunate turn of events for those still aboard because they don't have sufficient supplies to make port anywhere. They head back to Papeete, Tahiti, the closest port. Everyone knows, however, that they will starve to death before the reach port.
By miraculous good fortunate, they stumble upon an uncharted island before they reach that undesired fate of starvation. An angry Christian lives there named Attwater. He lives there with his servants, harvesting pearls. Due to the smallpox outbreak in that area, he is left with only four servants. Still ruled by greed, the three miscreants - Davis, Huish, and Herrick - plot to steal Attwater's pearls from him. Fortunately for Attwater, however, he sees through them. Huish's drunken mumblings give the scheme away, and Herrick's guilty conscience is evident. Attwater and his men drive them back to the ship.
Consumed with guilt, Herrick jumps overboard and tries to drown. He fails, though, and swim ashore. He begs for mercy from the proud and Puritanical Attwater. Meanwhile, Huish convinces Davis to trick Attwater into meeting under a truce but with the intention of killing him by throwing acid in his face. At the meeting, Attwater catches on once again and forces Huish to spill the acid upon his own face. Finally, he turns to Davis and threatens his life as well. Placing himself on a level with his divine object of devotion - Jesus Christ, - however, Attwater tells him to "go and sin no more."
After two weeks pass, Attwater's ship arrives on the island. The surviving crew members, Davis, and Herrick prepare to leave at long last. By this point, Davis has become a deeply religious person, to the point of fanaticism. His pardon by Attwater convinced him to turn to Christianity in order to change his life completely. Committed to his new-found cause and sense of peace, he is trying to convert Herrick as well. The book ends without revealing Herrick's persuasion whether in favor of religion or no.
