Nine-year old Pong, a resident of Namwon Prison, knows that life isn’t fair. Because his mother was a prisoner at Namwon when he was born, Pong must spend his childhood at the “reform center” until he reaches the age of 13. The government of their city, Chattana, believes that children born to criminals will become criminals themselves without intervention. Namwon is a miserable place where the oldest and biggest children abuse the younger ones while the guards turn a blind eye to the violence. Pong and his best friend, nine-year old Somkit, are at the bottom of this pecking order and find solace in one another.

At the center of Namwon’s courtyard lies the mango tree with its sweet, tantalizing fruit. The children of Namwon fixate on the tree, desperate for just one of its fruits. They are not allowed to climb the tree and must wait for the mangoes to fall by themselves. But by the time they do, it’s usually too late; the mangoes are already rotten. Pong possesses a unique aptitude for observation, and through careful study he can pinpoint the ripest mangoes and predict the precise time of their falls.