Jim Marlowe, the first mate aboard the ship Star of Brazil , takes command after his captain suddenly dies. After putting down a mutinous crew and extinguishing a fire, Jim sees the passenger vessel safely to port. Jim is given a commendation for bravery, as is his bosun, "Dusty" Johnson, and Jim receives the admiration of Ruth Denning, whose father was the first captain Jim served under on the S. S. Astoria . Unfortunately, Jim is held liable for an illegal load of gunpowder found aboard the vessel, and is blacklisted. He is eventually hired as the captain of the now aging civilian vessel, Astoria , but is unaware of the owners' plan to sink the ship to cash in on an insurance claim. Dusty signs on as first mate after passing his exams, and Jim's wife Joan is thrilled to finally get to join her husband on an ocean voyage, especially as she also has lustful notions about Dusty. Before departing, Ruth and Joan meet, and as Joan recognizes Ruth's love for Jim, Ruth realizes that Joan does not really love her husband. After the ship finally sets sail for Valparaiso, seaman "Chips," who is working for the owner, reports a leak in the hull that he created himself. Jim orders chief engineer McDuffy to start the electric pump, but McDuffy has dismantled it, so the sailors use hand pumps. When the pumps are sabotaged, Jim realizes he is in the midst of a racket to sink the ship, but refuses to give up. Chips knocks Dusty unconscious and leaves him to drown in a hold rapidly filling with water. Chips locks Jim in with Dusty when he goes to rescue him, but first mate Bill MacKeechie rescues them, at the cost of his own life. Before he dies, however, Bill confesses to Jim that he was reluctantly involved in the insurance fraud scheme. A severe storm hits the crippled ship and Joan becomes drunk when Jim sabotages the life boats so she cannot abandon ship along with the mutinous sailors. In her stupor, she reveals her sordid past as taxi dancer Gertie Swenson, "the sailor's delight." McDuffy reports to Jim that he built a pump out of the ship's generator, and Jim sees the ship safely to harbor. Jim is hailed as a hero, offered command of a brand new passenger liner, and Lloyd's insurance company gives him $10,000 for saving the ship. In Valparaiso, Joan tells Jim to mail her the divorce papers, and she saunters off with a local named Carlos. Jim, Dusty and McDuffy go into the bar for a celebratory drink, but when Jim gets a congratulatory telegram from Ruth, he immediately responds.