After learning that their mother might still be alive, Kick, Bert, Scruff and Pin have vowed to search for her. They'll comb the whole world if they have to! But it seems Mum's last-known location was closer to home.

With a bewildered Uncle Basti in tow, and their mysterious friend Bone determined to tag along, the kids set off for Sydney. The clues lead them to a place the Caddys have dreamed of visiting: the spectacularly noisy, gloriously exciting Luna Park. But it's not just fun and games they encounter here. What big surprises are in store?