Boy in the Striped Pyjams, Level 4

One day, Bruno's father gets a new job, and the family have to move from Berlin, Germany, to a new place. There is a strange camp at the end of the garden. Bruno is very unhappy and bored until he meets Shmuel. The two boys become very good friends. But why is Shmuel in the camp? And why is he wearing striped pyjamas? -Abridged
Level A2+