This compact chiller is the kind of clever, subtle blend of horror and sci-fi elements that could have only come from the mind of Richard Matheson. The Stranger Within is a highly effective piece of work because it never overplays its hand. Matheson's script is subtle, building tension in a methodical but effective manner as Barbara Eden's behavior gradually moves from eccentric to dangerous. It also grounds its fantastic concepts in the complexities of how her condition affects her marriage. Eden delivers a strong, sympathetic performance as a woman in the grip of forces beyond her understanding and George Grizzard does a great job of conveying the battle between love and frustration in the husband's mind as his character struggles to come to grips with the bizarre situation. There's also reliable support from Nehemiah Persoff as a doctor who is stymied at every turn by Eden's constantly-evolving condition. Lee Philips' direction is stylish without being fussy: he wisely hangs back and allows the actors to breathe life into the story, adding the occasional well-judged flourish when needed. He also assembles a chilling finale from deceptively simple elements. Finally, the film benefits from a lovely yet eerie keyboard-driven score by Charles Fox. All in all, The Stranger Within is a strong example of the 1970's made-for-TV film and well worth the time for horror and sci-fi fans.