An old legend tells of a fortune in gold hidden in the "Cañon del Oro" ("Canyon of Gold"), later called the "Lost Adams", guarded by Apache spirits. A man named Adams is said to have found it when he was young, only to have the Indians capture and blind him. Years later, Marshal MacKenna is ambushed by an old Indian shaman named Prairie Dog, and is forced to kill him. MacKenna thereby comes into possession of a map to the treasure. He examines it before burning it. Mexican outlaw John Colorado and his gang have been tracking Prairie Dog to get the map; they are themselves being tracked by the US Cavalry. They take shelter in the house of an old judge in Hadleyburg, kill the judge, and kidnap his daughter, Inga. Colorado captures MacKenna, intending to force him to lead them to the gold. The gang includes Colorado's right-hand man Sanchez and several Indians, among them an Apache warrior named Hachita and a fiery Apache woman, Hesh-ke. Hesh-ke and MacKenna were once lovers, but she rejected him after he arrested her brother, who was tried and hanged. Ben Baker, a gambler who knows Colorado, arrives with assorted townsmen who have learned about Colorado's plans when one of Colorado's men got drunk in town and said too much. Colorado is forced to allow them to join his party. The townsmen include the blind Adams himself. MacKenna warns them to return home, that they will just get themselves killed searching for gold that does not exist, but Colorado reveals that MacKenna shot Prairie Dog, and they stay. The cavalry, led by Sergeant Tibbs, ambushes the party at a water hole, and most members of the gang are killed. The remaining gold hunters continue on their way, and as they near the canyon MacKenna and Inga begin to fall in love. A jealous Hesh-Ke now wants MacKenna back. When the cavalry patrol is whittled down to just Tibbs and two others, Tibbs kills them and joins the gang. After a shoot-out with the Apaches, they reach "Shaking Rock", a feature on the map. Ma