Let's Scare Jessica to Death (1971)

After a stint in a psychiatric facility Jessica, her husband and a friend move to remote farm they have recently purchased. There they find a young woman by the name of Emily living in the house and they invite her to stay. When Jessica goes for a swim in the lake, she sees a body just below the water's surface. When they go into the village to sell some old furniture, they learn that a woman by the name of Abigail Bishop drowned in the lake and her body was never found. Local folklore has that Abigail is now a vampire roaming the countryside. A mute blond girl leads her to the body of a dead man but the body is not there when Jessica goes for help. Jessica and those around begin to wonder if she is losing her mind.