The Stones of the Moon — Judy Allen

It is mid-July, the time of year governed by Cancer - the moon's sign. David's archaeologist father is excavating a Roman mosaic found in Yorkshire. David becomes fascinated by an ancient stone circle on a nearby hillside, but his interest turns to a pervading fear when he touches the stones and gets a powerful electric shock. He befriends Westwood, who has a theory that the stones were used in ancient times to call forth water by chanting 'til the vibrations hit a powerful resonating note. Hence the name 'weeping stones'. And after centuries asleep, something has re-activated them.

David's father dismisses Westwood as an eccentric dabbler, and the townspeople throw him out as suspicious and untrustworthy. But Westwood's theory predicts a catastrophic flood - unless David can convince everyone of the stones' extraordinary force, find out what has woken them and turn the power back ...