Unearthly Stranger (1963)

In 'Unearthly Stranger,' an alien race sends a female agent to Earth to find a male human with whom she can mate and produce an alien offspring. The agent assumes the identity of a scientist's wife and tries to find a suitable mate. As she becomes more desperate, her behavior becomes increasingly odd and suspicious. The scientist begins to suspect that something is not right, leading to a thrilling and suspenseful climax.