Evil has many guises. Jack Taylor has encountered most of them but nothing before has ever truly terrified him until a group called Headstone rears its ugly head. An elderly priest is viciously beaten until nearly dead. A special needs boy is brutally attacked. A series of seemingly random, insane events even has the Guards shaken. Accepting the power of Headstone, Jack realises that in order to fight back he must relinquish the remaining shreds of what has made him human - knowledge that may have come too late to prevent an act of such ferocious evil that the whole country would be changed forever - and in the worst way.