By the time Ursula arrives home—stopping along the way at the grocer, the newsstand, just an ordinary Berlin woman making her morning rounds—and decodes the messages inside the bag, she’s forgotten about Mutti and the vivid, half-remembered dreams of the night before. Which makes her shock all the greater when she reads the third message, received from a radio operator near Bremen on a relay from Denmark, originating in Scotland, from somebody code-named Dunnock who works in G section. She reads it three times, and even then she has some trouble understanding what it means. Boiling down this meaning to a single devastating essence.

Mutti and Mr. Thorpe have a son who is imprisoned in Colditz.

For four years now, Ursula has maintained a network of friends whose loyalty to humanity exceeds their loyalty to Germany, who are willing to commit treason in order to provide a bed or a meal to a downed airman, or a Jew, or another agent whose identity has been discovered. This is dangerous work in the occupied countries of Europe, where most of the population hates the Nazis, but in Germany it’s suicidal. Ursula expects to die. She’s surprised she’s still alive, in fact. She continues to exist, day after day, only because of luck, or possibly the grace of God. (She debates this point with herself all the time.) But as long as she continues to live, she’ll dedicate that overdue life to rescuing others, to sending men and women from safe house to safe house, south toward Switzerland, where a few organizations exist inside that cocoon of neutrality to receive the fugitives. She can’t tell you why, exactly. Just that she must, that she cannot imagine herself otherwise.

To spirit a man out of Colditz, however, that was another story.

How did you extract someone from between the stones of Germany’s most notorious fortress? And then, once the alarm was sounded, smuggle him across the border to Switzerland? It was madness. It was impossible. Were this prisoner any other man, Ursula would refuse the request outright.

But he’s not any other man. He’s Mutti’s son, the son of Mutti and Mr. Thorpe, and Mutti is the only mother Ursula’s known. Mr. Thorpe is all she can remember of a father. So this prisoner, Benedict Thorpe, is her brother.

Still, the message is worded strangely. Instructions for reply are detailed and specific, routing through Scotland instead of London. The idea itself is crazy. It’s unprecedented. Ursula understands at once that Dunnock—whoever he is—possesses intimate knowledge of her past, considerable expertise in SOE operations, and no formal authority whatsoever. By any objective assessment, it’s probably a trap of some kind.