The Last Visitor (1969)

Having checked into Mrs. Walker's guesthouse in a quiet coastal village, Barbara is determined to enjoy her much needed break. She is woken that night by a mysterious man in her bedroom but Mrs Walker assures her he is one of the other two paying guests. The last two guests check out of the guesthouse but the sightings of the strange man continue. Determined to discover his identity Barbara lays a trap and finds the mystery man is Mrs. Walker who, still grieving the loss of her husband, re-creates him. Barbara later visits the old woman in a psychiatric hospital where Mrs. Walker asks Barbara to mail a couple of postcards...     addressed to her husband.