Summer 1643 England is at war with itself. King Charles I has fled London his negotiations with Parliament in tatters. The country is consumed by bloodshed. For Thomas Hill a man of letters quietly running a bookshop in the rural town of Romsey knowledge of the war is limited to the rumours that reach the local inn. When a stranger knocks on his door one night & informs him that the kings cryptographer has died everything changes. Aware of Thomas background as a mathematician & his expertise in codes & ciphers the king has summoned him to his court in Oxford. On arrival Thomas soon discovers that nothing at court is straightforward. There is evidence of a traitor in their midst. Brutal murder follows brutal murder. & when a vital message encrypted with a notoriously unbreakable code is intercepted he must decipher it to reveal the kings betrayer & prevent the violent death that failure will surely bring.