Asa and Rollo, acting on information they received from Ragni, the sorcerer, sail their invisible ship to Emperor Flood's stronghold, Castle Crag, to find out once and for all whether their parents are alive.
- ISBN10 0375848096
- ISBN13 9780375848094
- Publish Date 23 September 2008 (first published 18 September 2008)
- Publish Status Out of Stock
- Publish Country US
- Imprint Random House Books for Young Readers
- Format Paperback (US Trade)
- Pages 77
- Language English