E.C. Tubb 
Jondelle 
The Dumarest Saga Book 10

‘Earth is real, ‘ Dumarest insisted. ‘A world old and scarred by ancient wars. The stars are few and there is a great single moon which hangs like a pale sun in the night sky.’In the quest for his legendary birthplace, Earl Dumarest has traversed galaxies. Now, at least, he reaches Ourelle, a planet close to Earth — out along a far arm of the Milky Way. There he finds Jondelle, a boy who may hold the key to Earl’s search. But then Jondelle is kidnapped. And Dumarest’s pursuit of the imperilled boy leads him to a city of paranoiac killers — madmen whose terrible violence is always on a hair-trigger!(First published 1973)