December 1211. After thirty years as abbot of Saint Edmund's, Samson is dying. Before he takes his last breath, however, he calls Brother Walter to his bedside in order to recite the tale of the Green Children of Woolpit. This is a well-known local legend about two children who were found wandering in a Suffolk field half a century earlier. Samson also reveals he has recently been visited by a mysterious woman who claims a murder is about to take place. But Walter cannot find out who the woman is or anyone else who has seen her. Did she really exist or was she, like the green children, just another product of a dying man's imagination? Walter is reluctant to get involved but as he starts to investigate he realises there is more to both tales than first appears and eventually unmasks a tale of abuse and corruption going to the very heart of government. Can Walter finally solve the mystery of the Green Children of Woolpit and prevent a murder being committed, or is he already too late?