Christopher Boone, a fifteen-year-old boy with Asperger’s syndrome (an autism spectrum condition), is the protagonist of the story. He has an exceptional gift for mathematics but finds it impossible to navigate everyday human interaction. He notices the smallest details others overlook, yet struggles to understand the emotions of those closest to him. He cares deeply for his pet rat, Toby, but carries a Swiss Army knife in his pocket to defend himself from anyone who tries to touch him.
While investigating the mysterious death of a neighbour’s dog, Christopher inadvertently unravels a web of lies and immature choices made by his parents. As he changes before our eyes, he compels those around him to change as well. The solution to the dog’s death proves not to be the climax, but merely the starting point of the play’s central drama — a family one.