The Chrysalids, first published in 1955 by British writer John Wyndham.
An undetermined number of years into the future, post-apocalypse rural Labrador has become a warmer and more hospitable place than it is at present. The inhabitants of Labrador have vague historical recollections of the "Old People", a technologically advanced civilisation which existed long ago and which they believe was destroyed when God sent "Tribulation" to the world to punish their forebears' sins. The society that has survived in Labrador is loosely reminiscent of the American frontier during the 18th century, with a level of technology in use similar to the Amish of the present-day United States.
....
David and a few other children in the district harbour their own invisible mutation: they have telepathic abilities. The group are initially supported, advised and protected by David's moderate Uncle Axel, who comes to know about the group through some unguarded chattering when David is still small. Uncle Axel goes so far in his protection as to kill the husband of one of the group who was abusing his telepath wife, and about to blackmail the rest of the group.
