Lieutenant Parker reports for duty to Major Wilkins, commanding Ft. Sill, where Geronimo is a prisoner. Parker quickly wins the love of Pauline, the major's daughter, and the undying hatred of Captain Gray. The captain plans to release Geronimo in the dead of the night, throwing the blame on Parker. This he successfully does by obtaining, through an accident in the billiard room, possession of a letter from an Eastern friend to Lieutenant Parker. By tearing out a portion of this letter reading, "of course Geronimo's escape would mean an advancement to you," he successfully deceives everyone. But meantime Parker has been hurriedly detailed to find Geronimo; so Gray is sent out with a second detachment to overtake both Geronimo and Parker and make them both prisoners. Through a friendly orderly, Pauline learns of the trick. She hastens after Parker to warn him, but falls into Geronimo's clutches. The lieutenant is himself captured by Geronimo and, with Pauline, makes his escape. Later, he rescues Captain Gray and his command from certain death, and is rewarded by being made prisoner by Captain Gray. But all is explained at the formal court-martial, when Pauline rushes in with the other portion of the letter.