When John Haddrell dies of a heart attack at the wheel of his car, the woman is at his side is not his wife, but his lover Julia.

Recovering from her injuries Julia is visited by Margaret, who apparently knows nothing of the affair. Events take a sinister turn when Margaret begins to encroach on Julia’s life, engineering the dismissal of her home help and estrangement from her counsellor.  Left alone in the house Julia and Margaret are locked in deadly combat.