In a walled garden surrounded by skyscrapers, Father Michael Birney met an unholy end, stabbed by an assailant who invaded his vespers prayers and then vanished as twilight overtook the big city. A stone"s throw from the crime scene, a congregation of Satan worshipers chants its disturbing incantations -- an irony not lost on Detectives Carella and Hawes, who search among the cultists for a killer. But it will take more than a leap of faith for the cops of the 87th Precinct to expose the truth behind the deadliest -- and bloodiest -- of sins.