Cast & Crew
At a U.S. Navy laboratory where chemists have been developing an experimental new fuel, spy Paul Rattick breaks in and is shot and killed. Captain Wright of Naval Intelligence begins investigating the case, and after code breakers intercept a message instructing Rattick to report to Captain Roburt onboard the S.S. Vulcan , Wright assigns Tom Norman to impersonate Rattick. Later, naval operatives Dale and Farrell take some photographs of Tom, planning to publish them along with a newspaper article reporting Rattick's escape. To pull off his impersonation, Tom practices shooting with his left hand and playing the harmonica, an instrument that Rattick had played. Before Tom leaves for Sitka, Alaska, where the Vulcan is due to pick up Rattick, his sweetheart, Wright's secretary Mary Lynn, makes him promise to return safely. She then gives him a pistol disguised as a harmonica. Upon arriving in Sitka, Dale and Farrell give Tom a short-wave radio tucked inside a hard-cover book. Then, posing as Rattick, Tom boards the Vulcan and departs soon afterward. Later, after intercepting a message to Roburt instructing him to meet his contact, Edward Steele, in the harbor at Ketchikan, Tom uses his harmonica to send coded messages over the short-wave radio, which are received by Dale and Farrell, who have set up their radio equipment in a Sitka hotel room. When the ship anchors in Ketchikan, Tom sees a submarine approach and drop off Steele. Tom is called to Roburt's cabin, where Steele appears convinced that Tom really is Rattick. Later, Tom invites the ship's radio operator, Eric Balser, to his cabin to hear him play his harmonica, hoping that Balser will miss the important transmission that the spies are expecting. Tom then discreetly sets up his own radio equipment and begins sending an encoded message to Dale and Farrell using his harmonica. After Balser leaves, Tom is again called to Roburt's cabin, where Steele tells Tom that he will rendezvous in Ketchikan with Ehrlich, a spy whom he has met before. After they further quiz Tom about Ehrlich, Steele and Roburt begin to suspect that Tom is a counterspy. Just then, the engineer reports that a gas pipe has ruptured and flooded the ship with gallons of fuel. Hoping to verify his suspicions about Tom, Roburt asks Ehrlich to board the ship. Later, Steele intercepts Tom's radio transmission and orders the steward, Dajek, who is actually a Canadian government operative, to lock Tom inside his cabin. Instead, Dajek and Tom hide inside Roburt's cabin, and when Roburt, Steele and Ehrlich arrive, Tom shoots at them. After a lamp tips over in the ensuing scuffle, a fire ignites the pooled gas and the ship is consumed by the blaze. Tom escapes by diving into the water, while the spies either perish in the fire or are apprehended by the Coast Patrol. Tom recuperates in a hospital and is nursed back to health by Mary Lynn.