The Seventh Sacrament is the fifth in the Nic Costa series, David Hewson's detective novels of love and death in Italy.

There's an entire underground city down there . . . houses and temples, entire streets. I talked to a couple of the cavers Leo called in. They hero-worshipped Giorgio. The man had been to places the rest of them could only dream about.

Giorgio Bramante, a Roman archaeology professor, was master of the hidden world beneath the earth - until the day he lost his young son, Alessio, to a group of students intent on re-creating a centuries-old ritual to a long-banished god. His rage knew no bounds and, in a frenzy, he beat one of the students to death.

Released from prison fourteen years later, Giorgio is bent upon a terrifying revenge on all those he blames for the loss of his son. Inspector Leo Falcone, a member of the original investigating team, is one of his targets.

And Nic Costa, watching Falcone move relentlessly into the man's merciless grip, realizes the answer must lie in solving a cold case that, like the forgotten Alessio Bramante, has long been regarded as dead and buried for good.