Jennifer Welles and David Gale as "Dilys" and "Nigel".
A Weekend with Strangers (AKA Weekend Swingers) is a 1971 sexploitation film created by Chancellor Films, directed by Adam Savage. Notable cast members include Jennifer Welles (noteworthy adult actress) as "Dilys" and David Gale (Re-Animator's Doctor Hill and Soap Opera regular) as "Nigel" in starring roles, though many other actors are present. The film is described as being both of the horror/pornography genre. The only surviving footage can be seen in the form of the film's trailer, included in Something Weird's compilation Twisted Sex, Vol 1.
The official synopsis reads:
Dilys has delved deep into the strange and complicated world of weekend encounter groups. To her the Encounter Foundation Clinic — “dedicated to exploring the human potential” — was a haven, a place to give meaning and purpose to her life.
She was a respected and hard-working group leader at the Clinic until Nigel, a former lover and co-conspirator in an extortion racket, unexpectedly appeared and now threatens to expose details of her sordid past.
The price of his silence is a piece of information that he needs from Jenny, a member of the group. Faced with a serious scandal, Dilys is forced to co-operate. A karate-trained killer, an evil dope fiend and a lovely and seemingly helpless girl comprise the remainder of Nigel’s gang.
During the blackmail process, Dilys becomes intimately involved with Jenny and is reluctant to hurt her. She is also indirectly responsible for the death of one of the encounter group members.
Having completed her part of the bargain, Dilys realizes that she can no longer remain at the Clinic. She tells Nigel that she will go back to him. She manages to seduce him into dropping his guard and kills him, destroying his evil — and herself — in the process.