[2] Dr. Howard Vanard (John Carradine) implants a strange electronic component into the brain of returning Vietnam War veteran Joe Corey (Roy Morton), who becomes a psychotic killer.

Corey takes part in a jewel heist with a few cohorts, and while escaping from the scene, the stolen loot is hastily thrown from a rooftop into the back of a pickup truck belonging to a guy named David Clarke.

After he violently murders a cocktail waitress in a motel room and a secretary who is working late in an office, Corey goes in search of Dr. Vanard, seeking revenge for what the old arthritic scientist has done to him.

In 1969, Psycho A-Go-Go was totally re-edited, with additional footage featuring actor John Carradine as a mad scientist added, and the film was re-released by American General as The Fiend with the Electronic Brain.

[4] In that version, the Joe Corey character is a Vietnam War veteran who is mentally ill because a mad scientist named Dr. Vanard (John Carradine) experimented on his brain.

[9] As if the film hadn't gone through enough title changes over the years, Sam Sherman later released it to U.S. late-night television as The Man With the Synthetic Brain (with a violent nightclub singer's murder excised).

[10][11] Most of the elaborate musical nightclub numbers that appeared in Psycho A-Go-Go were also cut from Ghastly Horror since actress Tacey Robbins had retired from acting by 1971 and Adamson no longer had a need to promote her singing abilities.

[12] Dick Poston, a friend of Sam Sherman's who co-wrote the added material with him for Ghastly Horror, committed suicide several years later by purposely crashing the small plane he was flying in at the time.