Christopher, fifteen years old, has an extraordinary brain – exceptional at maths while ill-equipped to interpret everyday life. When he falls under suspicion of killing Mrs Shears' dog Wellington, he records each fact about the event in the book he is writing to solve the mystery of the murder. But his detective work, forbidden by his father, takes him on a frightening journey that upturns his world.

• National Theatre
• Luke Treadaway
• Niamh Cusack
• Paul Ritter
• Nicola Walker
• Una Stubbs
• Sophie Duval
• Nicholas Sidi
• Matthew Barker