Mother Ximenes' Handbook for Grade School Nuns features a story about a man who hasn't gone to Communion for years [St. Fidgeta & Other Parodies, 108].
The story continues: whenever he got sick he would call a priest, but every time the priest came, the old man would say "You can go away I feel better now." [One night the man becomes deathly ill and no priest answers the phone. The man sends his daughter off.] When she got there the rectory and church were dark and still. Then she noticed a little window in which a flickering red light was burning, but before she could try it a deep voice from behind the windowpane said, "Go home. There will be no priest for this man tonight." [The man runs home, telling how strange it was for a priest to say such a thing.] Later it was discovered the window was in the chapel! The old man died miserably, of course.
Bellairs goes to great lengths in setting up the punch-line for this story, one that Myers identifies as the Bellairsian variant on The Boy Who Cried Wolf. "I think the point of the story is that, because the little girl heard the voice from the chapel instead of the rectory (the priests' residence), it was the voice of God Himself that told her there'd be no priest tonight."
Bowen says that Bellairs didn't invent this story; it was told to Catholic kids everywhere. "I'm not surprised you were confused, because it depends on a basic bit of Catholic symbolism: the red light (a candle inside a glass cylinder that for some reason is always red) that is kept burning in the sanctuary of every Catholic church symbolizes the presence of God. I should explain (sticking to the past tense for safety) that, when bread was consecrated during the sacrifice of the Mass and became, in Catholic belief, the body of Christ, not all of it was consumed by the priest and people in the sacrament of Communion. A number of consecrated hosts (the name we used for the little wafers of unleavened bread) was kept expressly for the purpose of taking the sacrament to those who were sick or dying. It was necessary to keep them ready because, if word arrived suddenly that a parishioner was at the point of death, there might not be time to celebrate a Mass in order to consecrate a host for the purpose, and there was no 'quick way' to do it. So these consecrated hosts, looking in all respects like little discs of flat, white bread but on the deepest level of reality being the flesh of the Savior, were kept in a little cupboard called the tabernacle in the center of the altar, and the red light was kept lighted to remind the faithful to behave with proper reverence in the church and especially the sanctuary (the area where the altar was, behind the rail which all churches had at that time).
"So the point of the story is that the little girl mistakenly went to the window of the chapel (often a room in the priests' residence where Mass could be said) and what she heard was not a priest but the voice of God Himself telling her that the old reprobate would have no last chance to repent, and would therefore fry in hell as he deserved.
Myers also passes along an important hint: "Not every one of Bellairs attempts at humor hits its mark; in fact some of them miss by a mile."
