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Dr. Harlan Fiske has designed an electronic death ray device, which he and his assistants, Muller and Perez, have tested successfully. When Fiske demonstrates the device before War Department officials, however, it fails to work. General Darrow, commander of the "Devil's Dozen," the army flying squadron to which Fiske once belonged, does not believe that Fiske's invention can do what he claims it will. Meanwhile, Captain Robert Lawrence, an admirer of Fiske's daughter Barbara, and the designer of a new high-speed pursuit airplane, is told that test pilots have rejected his airplane because they have deemed it unsafe. Robert and Darrow both fly the airplane to prove them wrong, but while Darrow flies the airplane, a man is seen on a country road setting up a cannon-like projector similar to Fiske's. The man aims the weapon and fires it at the airplane, which then explodes in mid-air. Later, as part of the Army's investigation into the explosion, Robert is ordered to question Fiske about his device. Fiske insists that his weapon could not have been responsible for the tragedy because it was damaged during the failed demonstration for the War Department. When Roy Curran, a commercial pilot, borrows Robert's airplane, he too is sent to a fiery death by the mysterious ray gun. Robert is then taken off the investigation, but while visiting Barbara, he sees her father receiving a set of blueprints and becomes suspicious. Perez catches Robert trying to examine the blueprints, and when Barbara learns of it, she suspects that her sweetheart has been romancing her in order to get at her father's blueprints. After Robert is dismissed from the service for disobeying orders, Major Loy tells him that Fiske's feud with the Devil's Dozen resulted from his attempt to defend Drake, a pilot disgraced by accusations of cowardice. Later, Loy entices the mysterious killer to strike again by announcing that he will take to the air. The killer falls into the trap, and Robert and Loy, who are flying a bomber, cleverly outfox the ray gun and destroy it. When Fiske removes the injured ray gun operator from the exploded device, he discovers that the killer was Muller. Loy, however, recognizes Muller as Drake, and the killer then confesses that he duplicated the weapon in order to exact revenge on the men who disgraced him. He also confesses that he damaged the original weapon to divert suspicion away from Fiske. The mystery solved, Robert is reinstated in the army and resumes his love affair with Barbara.