THE MADAM AND THE SPYMASTER: The Secret History of the Most Famous Brothel in Wartime Berlin, by Nigel Jones, Urs Brunner and Julia Schrammel

The brothel owner Kitty Schmidt began to sneak portions of her savings out of Nazi Germany sometime in the mid-1930s, often by sending her girls to London with cash sewn in their underwear. By 1938, officials had caught on, but thanks to her police connections, she wasn’t formally charged with currency smuggling. Still, her time had come. If she wanted to flee the Third Reich, it had to be now.

A wealthy Italian client was poised to aid Kitty in her escape plan, but the telegram she sent him in preparation for her trip was intercepted and passed along to the SS functionary Walter Schellenberg.

Schellenberg, as fate had it, was searching for a location to serve as a listening post, a place where unsuspecting men inside and outside the Nazi ranks would be lulled into airing their disloyal thoughts in rooms rigged with microphones. The SS caught up with Kitty before she could cross the Dutch border, locked her in a windowless cell at Gestapo headquarters on Prinz-Albrecht-Strasse and abused her until she agreed to cooperate with Schellenberg’s scheme.

It’s a gripping story, and a largely unsubstantiated one. Although Schellenberg’s memoirs describe the existence of such an establishment, where all the staff, “from the maids to the waiter,” were spies for the Nazi regime, most of what we know is likely invented. In “The Madam and the Spymaster,” the journalists Nigel Jones, Urs Brunner and Julia Schrammel try to uncover the facts.

The mythmaking around Salon Kitty goes back half a century. In the 1970s, Schellenberg’s memoirs inspired the journalist Joseph Fritz (under the pseudonym Peter Norden) to write “Madam Kitty,” a novelized “true story.” Norden’s version of events was adapted in 1976 as a sexploitation film by the “Caligula” director Tinto Brass.

These twin products, particularly the blockbuster book, enhanced the legend’s notoriety if not its veracity. Viewers of the movie, in which Kitty teams up with one of her girls to destroy their Nazi overseer, would be forgiven for thinking that every character was a fiction.

Kitty, as the authors show, was a real woman, born Kätchen Emma Sophie Schmidt in Hamburg in 1882 to a salesman and his wife. In her early 20s, Kitty worked in Britain as a piano teacher; gave birth to a daughter, Kathleen; and married a Spanish man who later shot himself.

After World War I, Kitty brought her daughter back to Germany and opened her first brothel in Berlin. Commercial sex was effectively legal under the new Weimar government but became criminalized and heavily regulated again in the wake of its collapse. When Kitty opened a new establishment in 1935, she listed it as a hostel on official documents. Then the Nazis came calling.