A scientist, Dr Holander, takes his niece Miranda to Mexico in an attempt to reverse the effects of the alien DNA he used to create her. However the treatment goes horribly wrong, and sets Miranda on a killing spree as she sets out to find a mate.

Jerry Welbach, a reluctant bagman, has been given two ultimatums: The first is from his mob boss to travel to Mexico and retrieve a priceless antique pistol, known as "the Mexican"... or suffer the consequences. The second is from his girlfriend Samantha to end his association with the mob. Jerry figures alive and in trouble with Samantha is better than the more permanent alternative, so he heads south of the border.