'Now Susan,' Mother said, 'And you too, John. No night sailing. No going outside the harbour. And back the day after tomorrow. Promise.'But promises can't always be kept. Within twenty-four hours John, Susan, Titty and Roger find themselves fighting a night gale in the treacherous waters of the North Sea, adrift and in the main shipping lanes.
Suddenly, it's real adventure and only their sailing skills can help them now.