The Luna Laboratorium — N.J. Gemmell

Armed with the knowledge that their mom might still be alive, Kick, Bert, Scruff, and Pin have vowed to find her. They'll comb the whole world if they have to! But it seems that her last-known location was closer to home. So with a bewildered Uncle Basti in tow, and their mysterious friend Bone determined to tag along no matter what, the Caddy kids set off for Sydney. Secret tunnels and outback misadventures await!