This simple, though touching book follows Bruno, an eight year old German boy, through his short-lived experiences during World War II. His father, a commander in the Nazi army, moves the family (consisting of Mother, Gretel, and Bruno) to a three story house in Poland, a mere mile away from Out-With (Auschwitz) - the concentration camp he oversees. The camp is so close that Bruno can see the hundred (literally thousands) of people in striped pajamas (prisoners' uniforms) from his window. Unable to get sufficient answers from his his sister, "Hopeless Case" Gretel, his curiosity gets the better of him. He walks the tiresome distance from the house to the "Out Of Bounds At All Times And No Exceptions" barbwired fence.
There, he meets a young boy, Shmuel, of the same age, and the two quickly become friends. Only Shmuel is on the other side of the fence, the side that keeps people in, not out. Shmuel doesn't know why he and the rest of his family are there; only that they can't get out. Bruno goes to visit Shmuel daily, but never tells anyone of his activities, even under the heavy questioning of his sister.
Bruno soon learns the real reason, or what Gretel thinks is the real reason, that Shmuel (and the other people) are being held captive. They are Jews. Bruno never fully comprehends why the Jews are hated but the "Nothings," as Gretel put it.
The young boy journeys to the fence on a daily basis, and Shmuel often tells him about life at the camp; he hates it. Bruno, ever the adventurer, however wants to see for himself. One day Shmuel doesn't show up, or the next day, or the day after that. Bruno faithfully returns each day,however, in hopes that Shmuel will appear.
A week later, Shmuel shows up he looks even more tired than usual. He tells Bruno that his Papa has disapp; eared - he was taken on a march and hasn't eturned since; Bruno informs him that he will be moving back to Berlin the coming Friday.
Shmuel is heartbroken: first his father is missing, now his best friend is moving away. In a meager attempt at a going away gesture (partly to comfort Shmuel, but mostly to satisfy his curiosity), Bruno offers to help Shmuel find his father. His friend couldn't have been happier.
The appointed day arrives, only to be plagued by heavy rain. Bruno's mother won't let him leave the house. The rain soon stops, and Bruno races out of the house, donning his rain boots and and poncho. Bruno arrives at the gate and Shmuel is waiting, surprised by his friend's appearance. Bruno reluctantly changes into the prisoner's uniform that Shmuel has brought him, leaving his clothes in the ground outside of the fence.
Bruno crawls under the fence, and the pair walk back toward the main part of the camp. It is nothing like Bruno has imagined, and he immediately wants to return to his safe, comfortable home; he stays, however, and the two soon find themselves enclosed within a group of prisoners who are ordered to march.
Unable to escape, the two have no choice but to follow, in hopes that it will bring them closer to Shmuel's papa. It starts to rain and they are herded into a dark room. The door is closed in locked, but the two have no fear. They have each other.
A search is put out for Bruno, and his clothes are soon recovered. Father finds a gap in the fence, one small enough that a very small person - such as a young boy - can crawl under.