Based on a Texas Ranger comic-book hero who first rode into sight in 1948, this routine western is an Italian version of the adventures of Tex Willer (Giuliano Gemma), his sidekick Kit Carson (William Berger), and his Native American buddy Tiger Jack (Carlo Mucari). Predictably, Tiger Jack is nearly mute, and Tex wears a white cowboy hat, just to make clear which side he is on. A series of adventures take the trio into a confrontation with the Yaqui nation, intent on (finally) avenging the near-annihilation of their ancestors. To that end, the Yaquis rob a train, join forces with other Native Americans, and manage to concoct a secret weapon that is capable of immediately transforming their enemies into mummies. The "Lord of the Deep" is an alchemist parked at the bottom of a volcano, who creates a glowing green mummification rock (shades of kryptonite!).