A high-school friend asked if I could help him hunt down a story we read in grade twelve English, a few years ago.
His recollection of the story is decent. It’s told through the perspective of the mother (either third-person limited or first-person). The setting is 1950s-esque suburbia. The daughter keeps coming into the house to get kitchen stuff, saying it’s for someone who has promised the kids all kinds of good things if they help him. The mother assumes the person is an imaginary friend. She eventually realises, after an explosion, that the person isn’t imaginary, and hides in the attic with her husband. The story ends with the daughter bringing her “friend” up to see the parents.
There was a radio show that had that same plotline. I got it a few years ago on one of those classic collections of old sci-fi and horror radio shows on cassette. It creeped me out.