Bruno is a nine-year-old boy from whose perspective The Boy in the Striped Pajamas by John Boyne is told. The story starts in Berlin, but Bruno's father is a Commandant in the Nazi army and gets promoted by Hitler himself. This promotion comes with a new assignment: the commandant of the concentration (death) camp called Auschwitz. Bruno is naive and tells the story just as he sees and experiences it.
Bruno is out exploring one day and discovers another little boy sitting morosely on the other side of the fence. His name is Schmuel and he is exactly the same age as Bruno; they even share the same birthday. Their relationship continues over time, but eventually Bruno is going to be moving back to Berlin with his sister and mother and he wants to play at least one time on the same side of the fence with his best (and only) friend, Schmuel.
Schmuel has been unable to find his father (we deduce that his father has been exterminated), so Bruno agrees to come inside and help his friend look for clues. Schmuel brings Bruno a uniform (which Bruno refers to as "striped pajamas"), and Bruno fits right in since his head had been shaved because of lice--though he is "fatter" because he has, of course, been eating well.
The boys discover nothing as they explore the camp, but just as Bruno is considering sneaking back under the fence and go home, some soldiers come and round the two boys and some others up and herd them into
a long room that was surprisingly warm and must have been very securely built because no rainwas getting in anywhere. In fact, it felt completely airtight.
Bruno assumes the soldiers are just being nice and trying to keep this group from standing in the rain and catching colds. Bruno and Schmuel are glad to have each other as they wait together in the dark, neither realizing what is about to happen to them.
The next line of the novel says this:
Nothing more was ever heard of Bruno after that.
Obviously what happened is that Bruno, Schmuel, and the others the soldiers rounded up that day were gassed to death and presumably their bodies were then burned.