Actress Julia Blake, playing the nosy mother of Angela (Sigrid Thornton) in this film, appeared in producer 'Antony I Ginnane''s previous movie, also a thriller, as the nasty nurse in Patrick (1978).
In real life, this movie's lead actress Sigrid Thornton is married to this movie's 1st A.D. (assistant director) Tom Burstall. This picture was the first theatrical film the husband and wife collaborated on.