- Country: UK
- Genres: Horror
- Release: 1972-05-01
- Director: Robert Hartford-Davis
- Writers: Brian Comport
- Language: English
- Stars: Ann Todd , Patrick Magee (I) (1922–1982) , Tony Beckley , Madeleine Hinde , Suzanna Leigh , Percy Herbert , David Lodge , Ronald Allen , Maxine Barrie , Jeannette Wild
- Runtime: 92 min
- Awards: N/A
- AKA: The Fiend (Philippines) , Mummy Wouldn't LIke That (United Kingdom) , Beware My Brethren (United States of America) , The Fiend , Beware by Brethren (Norway) , The Fiend (United Kingdom) , Beware My Brethren (Canada) , El ritual (Spain) , The Fiend (Singapore) , Fanatismo diabólico (Argentina) , The Fiend (Germany) , Beware of the Brethren (United States of America)
- Plot: A religious sect called the Brethren has taken control of widow Birdy Wemys, sending her unstable son, Kenny, into a spiraling descent into madness. No woman is safe when Kenny's religious mania overpowers him and leads to murder and chaos.
- IMDB:tt0067094
Beware My Brethren Cast · · · ALL
Robert Hartford-Davis
Director
Ann Todd
Birdy Wemys
Patrick Magee
(I)
(1922–1982)
Minister
Tony Beckley
Kenny Wemys
Percy Herbert
Commissionaire Jim Hudson
Suzanna Leigh
Patricia 'Paddy' Lynch
David Lodge
CID Inspector
Ronald Allen
Paul
Madeleine Hinde
Brigitte Lynch
Jeannette Wild
Prostitute
Brenda Kempner
Congregation
Hani Borelle
Riverside Girl