This film adapts Melville's novel into a romance between Ahab and a parson's daughter. The screenwriter even re-wrote the beginning of the book and put Herman Melville's name on it.
An 1838 monument in New Bedford commemorates the victims of the white whale Moby Dick. As a ship arrives, Ahab (John Barrymore) shows off for the women before meeting Faith (Joan Bennett), the new parson's daughter. At the inn Elijah preaches against demon rum; Ahab drinks until the bar is closed for the Sunday meeting. Bored, Ahab goes to the church and hears Faith sing. Dressed up, Ahab calls on Faith, but Derek (Lloyd Hughes) complains to her about him and asks Faith to marry him. She says no. Ahab tells her he is leaving in the morning. At the ship Faith tells Ahab she loves him and will wait the three years to marry him.
At sea Ahab harpoons a whale; but after his boat overturns, he loses a leg. As the ship returns, Ahab is trying on his wooden leg. Faith comes on board to find him. Ahab says he won't hold her to her promise. When she sees the stump of his leg, she screams and runs away. At the inn Derek tells Ahab that she will keep her promise but indicates she is reluctant. Ahab says that Moby Dick is waiting for him too and sails away the next day without Faith getting a chance to tell him she loves him. Even after seven more years Faith tells Derek she still loves Ahab.
At Singapore Ahab buys a sailing ship. Against his orders the ship stops at New Bedford for supplies and more men. Ahab is obsessed with finding the white whale and leaves the next day without seeing Faith. The "heathen" Queequeg predicts they will find Moby Dick soon. Derek has been Shanghaied, gets seasick, whipped, and hears the name "Ahab." Captain Ahab tells the crew the boats will only be lowered for Moby Dick. Derek is not allowed to see him even though he says he is his brother. A terrible storm brings Ahab on deck, and Derek starts a mutiny. He chokes Ahab and throws a knife into his back; but Ahab throws Derek down, breaking his back. Ahab tells them to take care of his brother. About to give up, they see the white whale. Moby Dick bites a boat; but Ahab climbs on him and sticks his harpoon into his heart. The crew happily cuts up the whale, and Ahab says good-bye to Queequeg. Returning, Ahab calls on Faith, and they embrace happily.
Though Melville's themes are obscured by this sentimental story, Ahab eventually learns that Faith loves him in spite of his being maimed. Ahab's obsession with the great beast does not result in the humans' destruction but the whale's, which in a way is more true to life.