A friend of mine is trying to figure out the name of a short story that she read when she was younger. Approximate time is 1986-1988. Here's her recap of the story...

"I read a short story when I was a kid (it must have been somewhere from 1986-1988, by my estimate) about these kids whose parents met this guy named Mr. Natas. He would come to their house and give them bags of candy, and their parents would send them off to bed. One night the kids decided to look to see what went on after they went to bed and saw Mr. Natas leading their parents in a black mass. Turns out he was Satan, of course."

Anyone have any ideas what this story is?