Johan and his father have lived at sea for as long as Johan can remember. Or at least since he was three and his mother disappeared. Johan likes the ship. It has a greenhouse where they grow carrots, and it has fishing nets. Johan is good at diving and at mechanics, and helps his father repair the ship. One day when Johan’s father goes for provisions and Johan is left alone on the boat, he receives a distress call on the radio with a clue about his mother’s whereabouts...