An oil tanker burns at sea, and Molla Hansen, the captain's daughter, is the only survivor. She is rescued by lighthouse-keeper Silas Martin, who suffers fatal burns. He makes Molla promise to look after his orphan daughter, Pearl. Meanwhile, Molla's grief-stricken fiancé, Capt. Rodney O'Malley, departs on a long cruise. Two years pass. Pearl is seduced by rumrunner Charley Watts, and Molla learns of her pregnancy. Pearl implicates engineer Ira Meers as the man responsible, and Molla holds him at gunpoint at the lighthouse. Pearl then learns that Watts is already married and locks him in the lighthouse tower, fills it with gas, and hurls a lighted lantern at him. Pearl and Watts are killed, but Ira recovers. The explosion signals Rod's ship, and he and Molla are reunited.