Title: Is Underground (Wolves #8)
First published: 1993
Description: Dido's sister, Is, travels north to try and find her lost cousin. But instead of the promised Playland, she discovers an underground kingdom where children work as slaves in the worst conditions imaginable -- under the rule of the sinister "Gold Kingy".

Also published as plain old "Is".
Subjects: Juvenile fiction, Fiction, Adventure and adventurers, Coal mines and mining, Children's fiction, Fantasy fiction, Adventure and adventurers, fiction
Places: England
LC classification: PZ7.A2695 Is 1993