Mrs Allardyce was the guardian of Abigail.
Mrs Allardyce and Abigail were invited to the home of Mr R. He hoped to use Abigail as a medium to contact another plane through a ram's skull. Abigail was possessed by an evil entity, and was killed when the First Doctor and Edgar Allan Poe destroyed the skull. Mrs Allardyce and Mr R invented a story to explain Abigail's death. (PROSE: The True and Indisputable Facts in the Matter of the Ram's Skull)