Whoever Slew Auntie Roo? is a horror movie released in 1971. The story revolves around a wealthy and mentally unstable widow named Rosie Forrest, who lives in a secluded mansion. She has lost her daughter and has been deeply traumatized by the event.
Every year Auntie Roo, as she is known, hosts a Christmas party for children, where she dresses up as Mother Goose and distributes gifts and sweets. However, her real motive is to find a replacement for her dead daughter whom she believes will be reincarnated as a new child.
One year, a young girl named Katy arrives at the party with her parents. Auntie Roo becomes obsessed with her and begins to lure her into the mansion, using sweets and toys as bait. Katy's parents are suspicious and try to investigate but they are caught by Auntie Roo's accomplice, a man called Albie.
As Auntie Roo becomes more and more desperate to keep Katy, she starts to lose her grip on reality and becomes increasingly violent and abusive. Katy's parents decide to involve the police, but they are too late as Auntie Roo has already locked Katy in a secret room in the mansion.
Eventually, a group of children who had previously been lured to Auntie Roo's mansion by her are discovered in cages in her basement. The police finally arrive and arrest Auntie Roo and Albie.
The movie ends with Katy being reunited with her parents and Auntie Roo being taken away in a straitjacket, still convinced that her daughter will return to her.