Glenn Morgan, returning from Mexico to his mother and two brothers, Buddy and Jim, brings along his friend, Hugh Jeffries. Jeffries is extremely interested in the brothers' design for a superfast pursuit airplane. Jim, the oldest brother, is in love with Barbara Hawton, the daughter of his boss, Colonel Hawton. Although Glenn is also in love with Barbara and she with him, he feigns indifference when he learns about Jim's feelings. Just before he leaves with a delivery of mail, Jim proposes to Barbara and she gently turns him down. After he takes off, he is pursued by a masked Jeffries and his crony Marsh, who shoot down his airplane and steal the mail. Because Jim's body is not found, and the mail is missing from the wreckage of the plane, Glenn is positive that Jim has been murdered. Jeffries, however, spreads the rumor that Jim has absconded with the mail. This makes Glenn suspicious and he returns to Mexico to investigate Jeffries' background. Jim, meanwhile, has survived the crash and is being cared for by an old prospector. He begs the man to send for the colonel, but the prospector refuses to leave his claim. When Jeffries learns that Jim is still alive, he sends Marsh to drop a bomb on the prospector's cabin in order to eliminate the only witness to his part in the crime. Jim and the prospector are saved by hiding in the mine. Glenn returns from Mexico without the necessary evidence to accuse Jeffries of the robbery, so he and Buddy set a trap for Jeffries. Buddy hints to Jeffries that he is carrying a lot of money on this trip, and Glenn follows in the new pursuit airplane. After Glenn shoots down Jeffries, he lands, and finds Jim and the old man. Glenn proposes to Barbara and is accepted. To show there are no hard feelings, Jim asks to be best man at the wedding.