The Fiend U.S. Beware My Brethren is a 1972 British serial killer horror film, directed by Robert HartfordDavis and starring Ann Todd, Tony Beckley and Patrick Magee. The film is set against a background of religious fanaticism and, as with other films directed by HartfordDavis, also includes elements of the sexploitation genre of the early 1970s.
Kenny works two jobs, as a parttime lifeguard at a public swimming pool and a nighttime security guard. He returns from his nightshift to morning newspaper headlines screaming Third Nude Body Found He later goes to the swimming pool, where he sees it as part of his job description to berate female bathers for the skimpiness of their attire. Birdy meanwhile is in failing health a diabetic, she is dependent on insulin to control her condition but has to obtain supplies surreptitiously as the use of medicine is strictly forbidden by the Brethrens beliefs. A local nurse Brigitte Madeleine Hinde is hired to care for Birdy, against Birdys wishes, and becomes alarmed at what she sees of The Brethren. She passes on her concerns to her sister Paddy Suzanna Leigh, a campaigning journalist eager to write an expos of religious cults. In order to infiltrate The Brethren, Paddy decides to pose as an unmarried expectant mother seeking Gods forgiveness and redemption from her sins.Kenny descends into a frenzy of killing. One day at the pool, he is outraged when a young woman removes her bikini top and later follows her home to exact retribution for her Godless ways. While on his nocturnal beat he stumbles across a prostitute servicing a client, and she too is brutally despatched. Naked female bodies turn up across London in bizarre circumstances, dropping out of a cement mixer or dangling from a meat hook. ........
Source: Wikipedia