The She-Creature (1956)

The She-Creature (1956)

Following a hypnosis session at a party, a rash of murders leads the police to the professor who conducted the experiment, and eventually find that he inadvertently triggered his assistant to undergo a devolving process that reverts her back to the prehistoric creature she once was, and they race to stop the creature's rampage. (IMDB GL84)

Spike who was soon to become famous for playing
the title character in Old Yeller (1957)