Recommended reading - Crawlspace, by Herbert Lieberman (1971):

Crawlspace

By Herbert Lieberman.

Published by Pocket.

First published 1971.

First Edition.

Paperback.

ISBN-10: 0671775324

ISBN-13: 978-0671775322

Description:

In this novel of mounting suspense from award-winning author Herbert Lieberman, a terrifying surprise waits beneath a couple’s New England home. Albert and Alice Graves live a normal, if monotonous, domestic life. They never had children; they spend their days tending to their home and enjoying their time together.

One day, when the oil man, Richard, is refilling their furnace, Alice invites him to dinner, never suspecting that a casual act of charity will lead to a horrifying, morbid discovery in the crawlspace underneath their beloved house.

The Graves take Richard into their lives, becoming attached to his presence as though to the son they never had. Their town, though, is not nearly so welcoming. When the locals lash out against the Graves and their strange houseguest, the contented household is irrevocably drawn into a darkness they could not have imagined.