The Haunted House of Horror

The Haunted House of Horror, also titled Horror House and The Dark, was an early type of teen slasher film set in late 60s England. It starred Frankie Avalon and Jill Haworth as young adults looking for a thrill by spending the night in an old mansion in the English countryside. Although portraying a teenager, Avalon was nearlyyears old at the time of filming. It was directed by Michael Armstrong who would go on to direct Mark of the Devil.

They have fun exploring the mansion, even holding a seance before separating one by one by candlelight on the moonlit night. Sylvia, frightened by the mansion, leaves and hitchhikes toward home, but Kellet hangs behind at the mansion. While all the partiers are alone, Gary is brutally knifed his body is discovered by the panicstricken Dorothy and the others. Since some of them have a criminal record, Chris convinces the group to leave Garys body far from the home and to pretend that Gary left and no one knows where he went. They are all shaken by Chris assertion that one of them must be the murderer.During the next few weeks, the survivors are possessed by tension and guilt, and after Gary is reported missing, they are further shaken by questioning from the police. Kellet confronts Sylvia, learning that she may have lost a lighter that could link them at the mansion. He returns there where he is also killed. ........

Source: Wikipedia