I Was a Teenage Frankenstein

I Was a Teenage Frankenstein aka Teenage Frankenstein is a film starring Whit Bissell, Phyllis Coates and Gary Conway, released by American International Pictures AIP in November 1957 as a double feature with Blood of Dracula. It is the followup to AIPs box office hit I Was a Teenage Werewolf, released less than five months earlier. Both films later received a sequel in the fictional crossover How to Make a Monster, released in July 1958. The film stars Whit Bissel, Phyllis Coates, Robert Burton, Gary Conway and George Lynn.

Margaret, becoming suspicious of what is going on, decides to investigate and goes down to the morgue. She is panicstricken by the monster Gary Conway, who has been activated following the grafting of a new leg and arm. She dares not tell the Professor about her feelings and keeps silent for the present. On a couple of occasions, the professor takes discarded human body parts...and feeds them to an alligator concealed in a hidden chamber.One night, the monster leaves the laboratory. He peers into a girls apartment. The girl becomes hysterical and starts screaming in his attempt to silence her, he kills her in panic and flees. The next morning, the hunt for the murderer is on. Margaret, angry at the Professor, tells him that she knows that the monster is responsible for the murder. The Professor, taking no chanceshas the monster kill her and feeds her remains to the alligator. Dr. Karlton, sent out of town, knows none of this. ........

Source: Wikipedia