'Armed with the knowledge that their mum 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 Mum's 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!' (Publication summary)