It's been more than a year since Detective Sergeant Fiona Griffiths had any sort of murder case . . . when all of a sudden, she gets the call. A local archaeologist has been found bloodily murdered. Her head severed from her body. Her eyes apparently fixed on a fragment of Latin text. The crime seems to summon the ghosts of Dark Age Britain - and the shade of King Arthur. But why are those ancient enmities alive once again? Why are armed burglars raiding remote country churches? And how many more people will die before these clues are unravelled? Fiona thinks she knows the answers to these questions . . . but the crime that underlies them all is so utterly unexpected, so breathtakingly audacious in its execution, that it hasn't yet been committed.