Lieutenant Billy Boyle could have used a rest after his last case. But when his girlfriend Diana Seaton - a British spy - goes missing in the Vatican where she was working undercover, he insists on being assigned to a murder investigation there so he can try to help her. An American monsignor is found murdered at the foot of Death's Door, at Saint Peter's Basilica. Wild Bill Donovan, head of the OSS, wants the killing investigated. The fact that the Vatican is neutral territory in Germany-occupied Rome is only one of the obstacles Billy must overcome.
