The Godsend (1980)

Director: Gabrielle Beaumont
Cast: Angela Deamer, Angela Pleasence, Clarissa Young, Cyd Hayman, Joanne Boorman, Malcolm Stoddard, Patrick Barr, Wilhelmina Green

Synopsis:

An English family of six takes in a pregnant woman who disappears shortly after giving birth. They raise the baby girl as their own, but over the years the strange deaths of their children make them consider whether the little girl is more than she appears.