An American military officer discovers his superiors are planning a military coup.

U. S. President Jordan Lyman signs a nuclear treaty with the Soviet Union, arousing public displeasure and the disapproval of the military, particularly Gen. James M. Scott, Chairman of the Joint Chiefs of Staff, who considers the action almost treasonable. After Martin "Jiggs" Casey, Scott's aide, comes across some cryptic messages and learns of a top secret base in Texas, the existence of which is denied by others in the Pentagon, he suspects that Scott is leading the other Chiefs of Staff in a coup to occur seven days later when the President will be isolated from his civilian aides during a military alert. Casey reports his suspicions to the President, who sends Sen. Raymond Clark to investigate the secret base. Clark locates the base but is held there incommunicado until he breaks out with the help of an officer friend of Casey's. Presidential aide Paul Girard flies to Gibraltar, where he obtains a statement from Admiral Barnswell, a Joint Chief who isn't enthusiastic about the coup, but Girard is killed in a plane crash on the return trip, and Barnswell denies signing the statement. Later, Casey obtains some highly incriminating letters from Eleanor Holbrook, Scott's former mistress, but the President cannot bring himself to use them when he confronts Scott and demands his resignation. Scott, confident that public opinion is on his side and that his aides are behind him, refuses. The President goes on television to demand the guilty officers' resignations, and Scott's colleagues desert him. During the telecast it is learned that Barnswell's statement has been found in the plane wreckage, and Scott also resigns, squelching the coup before it occurs.