Bruno is a nine-year-old boy growing up during World War II in Berlin. He lives with his parents, his 12-year-old sister Gretel and maids, one of whom is called Maria. After a visit by Adolf Hitler Bruno's father is promoted to Commandant, and the family has to move to 'Out-With' because of the orders of "The Fury" (Bruno's naïve interpretation of the word 'Führer'). Bruno is initially upset about moving to Out-With (never identified, but cf. Auschwitz) and leaving his friends, Daniel, Karl, and Martin. From the house at Out-With, Bruno sees a camp. One day, Bruno decides to explore the strange wire fence. As he walks along the fence, he meets a Jewish boy named Shmuel, whom he learns shares his birthday. Shmuel says that his father, grandfather, and brother are with him on this side of the fence, but he is separated from his mother. Bruno and Shmuel talk and become very good friends, although Bruno still does not understand very much about Shmuel and his side of the fence. As the meetings go on, Bruno's naïvete shows that his innocence has been preserved despite being near a death camp.
When lice eggs are discovered in Bruno's hair he is forced to get all of his hair shaved off. Bruno comments that he looks like Shmuel, and Shmuel agrees, except that Bruno is different. Bruno's mother eventually persuades his father to take them back to Berlin and stay at Out-With without them.
The next day Bruno concocts a plan with Shmuel to sneak into the camp to look for Shmuel's father. Shmuel brings a set of prison clothes, and Bruno leaves his own clothes outside the fence. As they search the camp, both children are rounded up along with a group of prisoners to be sent to the gas chamber. Bruno apologizes to Shmuel that they didn't successfully find his father, which Shmuel does not have a chance to reply to before the gas is turned on, and Shmuel and Bruno both die. Bruno's mother and sister return to Berlin, and his father stays at Out-With, where he finally works out what had happened. When soldiers come to take him away from Out-With, he is happy to be leaving.