Whilst Sara Farnese pours over ancient texts in the silent Vatican reading room, a brutal murder is taking place in a nearby church. Then suddenly a crazed man enters the Vatican carrying a bloodied bag. He walks up to Sara's desk. He has something he would like her to see . . .

Soon Sara is inextricably linked to a series of horrific and cunning murders, each one representative of the death of a martyr of the Church. Into this charged climate enter Detectives Nic Costa and Luca Rossi, enlisted to track down the killer, and to protect Sara from the horrors he is capable of. It seems that at any time she could be the next chosen sacrifice.