Summer 1900: Leo turns 13. He's the guest of Marcus, a wealthy classmate, at a grand home in rural Norfolk. Leo is befriended by Marian, Marcus's twenty something sister, a beauty about to be engaged to Hugh, a viscount and good fellow. Marian buys Leo a forest green suit, takes him on walks, and asks him to carry messages to and from their neighbour, Ted Burgess. Leo is soon dissembling, realises he's betraying Hugh, but continues as the go-between nonetheless, asking adults naive questions about the attraction of men and women. How does innocence end?