I don’t recall if this was a  TV Movie or a TV series episode. I remember I had nightmares about it though when I was young. It was from the 1970’s. The basic plot was (as I recall) a family moved into a house and there was a painting on the wall (or the acquired the painting… not sure) of a winter scene. The kids (if I recall) could pass into the painting into this other world and met a man who lived in a cabin or small house in the winter scene. Turns out, the man had killed his wife (or someone) with an ax and had them in a burlap sack as I recall. The kids had a hard time convincing their dad that they weren’t making up the story… I don’t recall much else from it, but I do remember it being pretty scary.