So memorable is Bernard Herrmann’s whistled theme to Twisted Nerve that Quentin Tarantino wisely appropriated it to equal unsettling effect in Kill Bill: Vol. 1. While good, the British thriller itself is not close to being as “sticky.”

Hywel Bennett lost his penis in 1971’s Percy, but here, he loses his mind. As Martin, the young man fancies shifting into an alternate personality — that of the 6-year-old Georgie — in order to weasel his way into the life of Susan (Hayley Mills, The Parent Trap), a beautiful, 17-year-old librarian.

It works. In a real credibility-strainer, no matter the lengths taken by the screenplay to set it up, he goes to live with her for a week in the boardinghouse run by Susan’s single MILF (Billie Whitelaw, The Omen). Ingratiating himself to the fellow residents, Georgie refers to himself in the third person, laughs at burps, makes nonsensical jokes (“Batman is a fat man, ha-ha!”) and eventually dabbles in fatal stabbings.

Twisted Nerve is pinched by the permissiveness of its times. While it can do little more than hint at Martin’s suppressed homosexual urges and the Oedipal draw Whitelaw’s character feels toward Georgie, it operates on the theory that “mongolism” (now called Down syndrome) equates to psychopathic. Today, we know that’s not just poor science, but pure offense.

The title refers to “a ganglion gone awry,” and although director Roy Boulting (There’s a Girl in My Soup) is able to keep the film on its rails (thanks to the performances), it does become less and less special the more it drones on. It could be twice as suspenseful by losing a quarter of its two hours. —Rod Lott

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