The Years of the Wolf — Craig Cormick

This story begins with a murder. A German internee is found dead inside a civilian internment camp during World War One, and one young internee, Arno Friedrich, determines to find the killer. But the more he probes into the lives of his fellow internees the more he discovers that little within the old stone prison is as he had imagined. He finds that the Germanic facades and fantasies the men construct hide secrets within secrets. And a killer.