At breakfast time on Cloud Island, Teelo is shocked to discover a rat nibbling at his food bowl. Immediately, he gives chase -- all over the house, around the other animals living with him and Victor the Vet, out the door, and up a tree. He corners the rat on a branch that stretches far out over the water. Just as Teelo is about to pounce, however, he hears a loud CCCC-RACK as the branch snaps in two.
Teelo tumbles into the sea. He flails and sputters, and then scrambles onto a log floating by. Teelo shakes the water out of his eyes only to discover that the log is drifting away from Cloud Island, taking him with it.
For a day and a half Teelo weathers life adrift on the log. He discovers new creatures in this strange world: silvery salmon, furry, bright-eyed sea otters, little puffins, and huge gray whales. He spends a terrifying night alone, tossed up and down on waves as a storm passes through.
Rescue finally comes when a wooden sailboat glides alongside Teelo. A young girl with wide brown eyes, named Lilly, and her grandfather pull Teelo onto their boat. After a few days, Teelo gets his sea legs and adjusts to life aboard the sailboat. Despite Grandpa's allergy to cats, Teelo soon becomes a part of the crew.
One day their journey brings Cloud Island into view. To get a better look at his old home, Teelo runs right up to the bow. When a big wave knocks him overboard, Teelo once more finds himself in the ocean. This time he is washed up on the shore of his old home and into the midst of his old friends. Now Lilly and Victor must decide where Teelo really belongs.