Circleen goes on holiday to Turkey with her artist. Her chums Ingolf, Fredrik, and Viktor decide to go to see her, and stow away on board granddad's ship, where they meet another stowaway, the tough, fearless mouse Ali, who has set off into the world in search of happiness. Our friends are dragged into Ali's adventures and agree to help him to obtain cheese on board. But granddad is furious: he doesn't want kids on board, and the cat, the cook, and the captain aren't exactly mouse lovers either. Meanwhile, Ali has a secret!