Martin's school is no ordinary school. There are snowball fights, kidnappings, cakes, a parachute jump, a mysterious man called 'No-Smoking' who lives in a railway carriage and a play about a flying classroom. As the Christmas holidays draw near, Martin and his friends - nervous Uli, cynical Sebastian, Johnny, who was rescued by a sea captain, and Matthias, who is always hungry (particularly after a meal) - are preparing for the end of term festivities. But there are surprises, sadness and trouble on the way - and a secret that changes everything.