Felix Spark's little sister is a fixologist. Astrid can fix cracked cups, broken toys, Felix's thumb, even Dad's Harley Davidson when it gets mysteriously swallowed by a hole in the back lawn. But Astrid can't fix what's under the house, threatening to destroy the whole world, that takes a rock band, a didgeridoo, an astrophysicist and a few thousand echidnas. Suggested level: primary, intermediate.