When the young Ishmael gets on board Captain Ahab's whaling ship, little does he suspect that the mission on which he is about to embark is the fulfilment of his master's obsessive desire for revenge on Moby Dick, a white whale who has already claimed countless human victims and destroyed many fleets.

This novel began as a simple rewrite of an obscure little narrative, in which Israel Potter tells the story of his sad fall from revolutionary hero to London peddler. Following its opening chapter Melville's novel retells that tale, then alternately moves between invented episodes and historical sources unrelated to the original.