"When Michael Calls" is an ABC Movie of the Week from 1972 that belongs to that special group of made-for-TV chillers that everyone who saw still remembers as terrifying the life out of them. I'm pleased to report it still works even today.
A young divorced mother named Helen suddenly starts receiving prank phone calls that claim to be from her nephew Michael, crying and asking for help. Trouble is that Michael has been dead for years. As the calls continue, people around Helen start to get murdered.
Although the movie as a whole is fairly low key, the first 30 minutes or so are really effective. The calls from "Michael" are genuinely creepy, and on first viewing, there really does seem to be no rational explanation for them. This sets up a great sense of unease for the characters and viewer alike. Elizabeth Ashley does a great job in the lead role as Helen, in fact all of the acting is good, including her young daughter. Gradually the mystery is explained, but you won't hear a spoiler from me, so I recommend seeking out a copy of this. The opening premise is so good and so spooky, that it will certainly make you curious to watch it to the end.