Watch HDToday. During WWI, the Germans try to encourages and hires a band of certain Mexican guerrillas and bandits to make trouble on the Texas border and attack the Stonewall Farm. He plans this so the Americans will have no choice but to send more troops to Texas instead of Europe. Masterminding the plot is a German spy who has, at his disposal, the RX4, a specially equipped weapon-bearing automobile of awesome speed, but a U.S. Army lieutenant carries the day with his own fleet of Model T racers.