The Dark Angel (Monika Ritter #8)

Hiding out at a monastery outside Hallein, Sarah and Monika wait for Viertel and two other agents to return to Austria to investigate the rumored redoubt in the Alps—a network of underground bunkers and factories where the Nazi hierarchy plans to retreat when the Allies invade Germany. After being denounced by an informant and surrounded in a mountain farmhouse, Viertel and his companions must decide whether to try to escape or die with the top-secret information they hold. Then Viertel will begin a desperate race against time to reach Monika and Sarah at the monastery to warn them that the Gestapo agents are coming.

After Sarah and Kuen are sent to investigate what happened to Viertel and the other agents, a Gestapo chief sets a trap to corner them. Obsessed by Monika, or The Dark Angel, as she is known within the ranks of the Nazi secret police, the Gestapo officer will stop at nothing to find her. And when Monika realizes the world she and the others have constructed is about to collapse, they will be forced to take extreme action to preserve not just their own lives but those of every man, woman, and child hiding in the monastery.