The Fiend with the Electronic Brain was a re-release of Al Adamson's Psycho A Go-Go featuring new footage starring John Carradine that re-imagined the original film's story with a sci-fi plot.

Maria San Carlos, the only daughter of a wealthy landowner, is betrothed to Escobar, a General in the Mexican Revolution, but she does not love him. Escobar sends a mixed gang of Americans and Mexicans to capture her and bring her to him. Complications ensue when an American cowboy, who had been hitching a ride with Maria's entourage and has his gold stolen by the gang, pursues them across the desert.

Jewel thieves quickly dispose of the loot when the alarm is raised, then track down the family upon whose truck they threw them, meanly interrogating them in the hope of getting them back.

A mad scientist implants an electronic device into the brain of an injured soldier, which turns him into a psychotic killer.