Wonder Woman stops an attempt by enemy spies to sabotage the U.S. Navy's new submarine called "The Octopus".
Wonder Woman, as Diana Prince, attends a christening of a new U.S. submarine, the "Octopus." Diana goes to break a bottle over the hull, but realizes that the bottle contains an explosive, so she hurls it away instead. A group of Nazi agents who have been watching for the explosion from their own boat, realize that their plan has failed, but decide to steal the Octopus for themselves. They somehow trap the submarine on the bottom of the ocean floor.
Steve Trevor is distraught to realize that his friend, Ensign Martin, is suspected of planting the explosives in the bottle, as he brought the bottle to Diana and has now disappeared. Steve insists that his friend is trustworthy, and is determined to figure out what is really going on. He notices some flashes coming from a nearby boat (the one where the Nazi agents are watching the events), and realizes that Martin is using Morse Code to signal for help. Diana also sees the flashes and soon she, as Wonder Woman, and Steve get in a speed boat and head towards Nazi craft.
The Nazi's, still watching from their own boat, give an order to tamper with the air supply on the Octopus. This spurs Martin to action, but the Nazis overwhelm him and, after tying him up, toss him into the ocean. Steve and Wonder Woman spot him and rescue him, and soon the three of them board the Nazi boat and defeat the enemy agents. The agents try to escape by jumping overboard, but Etta Candy arrives with the Holiday Girls and captures them.
Wonder Woman dives into the ocean to find out what is happening to the Octopus. She realizes that the Nazis are using a magnet to trap the submarine on the ocean floor, and are pumping carbon dioxide into the air supply. They have send a squad of divers to board and claim the submarine once the U.S. crew is unconscious. A lone U.S. diver has been sent to investigate the submarine's problems, and the Nazi divers attack him. Wonder Woman intervenes and saves the U.S. diver, bringing him safely back to land.
She then returns to the water and finds a German submarine that is acting as the staging area for the Nazi divers. She allows the Nazis to bring her on board, then makes quick work of them and of their submarine. This breaks the magnetic field that has trapped the Octopus, which is then able to escape the invading party.
Wonder Woman alerts the U.S. General of the presence of the now powerless Nazi submarine, and he sends U.S. forces to capture the Nazi agents. Meanwhile, the Octopus is in perfect working order and its launch is a success.