It's March 1889. It is midnight. Six strangers meet for the first time outside the great door of Tewkesbury Abbey, their mission to enter the sacred building and seek out the tomb of the medieval crusader knight, Sir Roger de la Pole. What they find inside however, is both unexpected and deeply shocking. Detective Inspector Ravenscroft and Constable Tom Crabb are called upon to solve the crime and to decipher the strange coded letters on the outside of the templar's tomb. Soon they will discover that the solution to both mysteries stretches back far into the past and that their origins lie in two distant lands...