Tragic Ceremony (1972)

Four young people are enjoying the easy life, cruising on a yacht in the sun. Returning to land their car runs out of fuel and they find themselves outside a large manor belonging to Lord and Lady Alexander. Hoping to find fuel they are invited in to stay the night and shelter from a heavy storm. The three men are put up in the servant's quarters while Jane gets a room in the house. Hearing a strange noise she heads down stairs, finding the Alexanders performing a black mass and she is put onto the altar to become the sacrifice.