Winter 1940: With soldiers parading down the Avenue des Champs-Élysees, Nazi flags dangling from the Arc de Triomphe, and the Eiffel Tower defaced with German propaganda, Parisians have little to celebrate as Christmas approaches. Police Inspector Henri Lefort's wishes for a quiet holiday season are dashed when the Gestapo orders him to investigate the disappearance of Dr. Viktor Brandt, a neurologist involved in a secret project at one of Paris's hospitals.

Being forced onto a missing persons case for the enemy doesn't deter Henri from conducting his real job. A Frenchman has been beaten to death in what appears to be a botched burglary, and catching a killer is more important than locating a wayward scientist. But when Henri learns that the victim's brother is a doctor who worked at the same hospital as the missing German, his investigation takes a disturbing turn.

Uncovering a relationship between the two men—one that would not be tolerated by the Third Reich—Henri must tread carefully. And when he discovers that Dr. Brandt's experimental work is connected to groups of children being taken from orphanages, Henri risks bringing the wrath of both the SS and the Gestapo upon himself and everyone he loves.