The Angry Breed (1968)

In Vietnam, aspiring actor Johnny Taylor is given a prize film script after saving the life of a Hollywood screenwriter. On his return, Johnny has trouble finding a studio that will let him play the lead until he saves producer Vance Patton's daughter Diane from a cycle-gang attack. The grateful father sends him to agent Mori Thompson, but Thompson wants the script for gang leader Deek Stacy. Deek and his agent feed Johnny LSD and drag him away to the dungeon during the producer's Halloween party. Melody Patterson (married at the time to James MacArthur) plays April Wilde.