Whoever Slew Auntie Roo? (1972)

Mrs Rosie Forrest, aka 'Auntie Roo', has a holiday tradition of inviting orphans to her mansion for a party. But Roo isn't completely sane; she lost her husband and is obsessed with her deceased daughter, whose corpse she still keeps in the house. When Katy Coombs sneaks into the party with her brother, Christopher, the deranged biddy abducts the young girl with the hopes of replacing her daughter.