Behind Locked Doors (1968)

Two women attend a party in a barn, where they meet Mr. Bradley, a strange middle-aged man with a British accent. He saves one of them from an attempted rape in a hayloft, so she introduces him to her friend Terry. After chatting a while, he leaves and drains the gas from their car. Finding their gas tank empty, Ann and Terry walk until they come to Bradley's isolated house, where he lives with his sister Myla and a servant named Freddy. It turns out that Bradley is actually an insane mortician and that he have certain plans with his guests.