The Pledge by Joel Agee
"'It's a promise, Frau Moser,' the inspector said, impelled solely by the desire to leave this place. "'On your eternal salvation?' "The inspector hesitated. 'On my eternal salvation,' he finally said. What else could he do? When a young girl is found brutally murdered in a Swiss mountain forest, the brilliant Inspector Matthai can't put the case behind him. Not even when a local felon is arrested. Not even once the suspect has confessed. Matthai promises the girl's mother that he will stop at nothing to find the real killer. Adapted into a Hollywood film, The Pledge is the chilling story of a man in desperate search of the truth. A man driven to sacrifice everything, to commit acts of cruelty and obsession in a desperate search for a killer he can't find.