A shipment of government gold is lost when the pack train headed up by famous scout Kit Carson is wiped out. Only Carson miraculously escapes. Aided by a detachment of cavalry, Carson rounds up the outlaw band known as the Mystery Riders. Carson then leaves the soldiers and his Indian friend, Nakomas to bring in the prisoners, and rides furiously back to the trading post, where his little friend, Joan Fargo, disguised as a boy, has been keeping watch on Kraft, the man who Carson suspects is the secret leader of the Mystery Riders. When he is accused of being the leader of the Mystery Riders, Kraft swears his innocence and makes a quick getaway. In order to trap him, Carson and the troopers don the garb of the Mystery Riders with hope that Kraft, upon seeing his men, will be fooled into giving away the location of his secret hiding place for the gold.