"There were letters carefully tied in a ribbon," said Hoerlin, 72. "It was clear they were love letters."
There were 500 in all: 400 written by her mother and 100 by her father from 1934 to 1938, while she was living in Berlin and he in Stuttgart.
Hoerlin began reading.
They filled in the blanks of a story that her parents would not discuss. Hoerlin was determined that it would not be forgotten.
She chronicled their experiences in her recently self-published book, Steps of Courage: My Parents' Journey From Nazi Germany to America.
"This is a story embedded in history: the rise of Hitler," said Hoerlin, who taught public health at the University of Pennsylvania and Haverford College and was acting health commissioner for Philadelphia in the 1980s.
"Those letters were a document of that, and my parents' love story."
It took Hoerlin four years. She spent hours in her study translating the letters from German. She traveled abroad to scour German archives. She interviewed historians.
Hoerlin's book uncovers what historian Frank Mecklenburg described as an "unusual constellation" of events and people in Nazi Germany.
The story is "sort of typical in a way, and also not typical," said Mecklenburg, director of research at the Leo Baeck Institute in New York, a research library and archive on the history of German-speaking Jews.
Commonplace, in some ways, was Schmid's background as a Jew who did not grow up in an observant household and later converted to Catholicism when she married. Her first husband, Willi Schmid, was a well-known literary and music critic.
Until 1933, German society was characterized by a "push toward" and a secularization of the culture, Mecklenburg said. Religion was secondary.
But Hitler began to change that. On June 30, 1934, known as the Night of the Long Knives, his troops rounded up and killed people they viewed as government opponents. Willi Schmid was slain in a case of mistaken identity.
Within weeks, Kate Schmid met Hermann Hoerlin.
Schmid had been the press representative for a 1934 German mountain-climbing expedition to the Himalayas that ended in the deaths of 10 people. Hoerlin, a record-setting mountain climber, was sent by the German Alpine Club to provide Schmid with expert information as she handled reports on the tragedy.
Soon, the charming and vivacious mother of three and the reserved athlete studying to be a physicist fell in love.
"You have intoxicated me with the quietest things," Schmid wrote in a letter to Hoerlin. "Let it always be so."
They courted as conditions for Jews worsened. Although Schmid had converted to Catholicism, she was classified as Jewish by the government. The Nuremberg laws were enacted in 1935, and a union between them was forbidden. They resolved to marry and leave Germany.
"Nothing good can follow from our being categorized by blood," Hoerlin wrote to Schmid. "That premise can be maintained by people who - to put it mildly - are thickheaded."
The couple's story then veered toward the extraordinary.
Schmid met repeatedly with high-ranking officials in the Nazi government, first to demand reparations after her husband's death. She was given a monthly stipend, and Rudolf Hess himself visited her to apologize for the government's mistake.
Later, Schmid sought to reclassify herself as half-Jewish when she discovered her biological father was a Prussian count. Finally, she sought the government's permission to marry, as well as its help in securing a job for Hoerlin in the United States.
Sometimes Schmid left government headquarters shaking with fear.
This is "exceptional. It is not your typical German-Jewish Holocaust experience," said Juergen Matthaeus, director of applied research at the U.S. Holocaust Memorial Museum.
The man who most helped the couple was Fritz Wiedemann, a commanding officer who served as Hitler's adjutant, or personal assistant. Wiedemann had accompanied Hess on his earlier visit to Schmid.
Hoerlin theorizes that Wiedemann helped out of empathy for the couple's situation and lingering regret over the killing of Schmid's first husband.
Wiedemann also helped another Jewish family and several Jewish soldiers escape, said Tom Weber, author of Hitler's First War: Adolf Hitler, the Men of the List Regiment, and the First World War. Wiedemann later testified against Nazi leaders in the Nuremberg trials.
On July 12, 1938, Schmid and Hoerlin married in Berlin and on Aug. 9 sailed for New York, where Hoerlin had secured a job with a film-manufacturing company.
The couple went on to make a life for themselves in New York, and then Santa Fe, N.M., where Hoerlin worked at the Los Alamos National Laboratory studying the effects of high-altitude nuclear testing. He also was the subject of a U.S. investigation during the McCarthy era because of his membership in the American Civil Liberties Union and his friendship with Paul Robeson.
Hermann Hoerlin died in 1983, and Kate Schmid Hoerlin two years later.
"It was luck, their considerable charm, and valuable friendships," Bettina Hoerlin said of her parents' long union. They had "a willed optimism that they were going to suceed in getting married, getting out, and having a life together."
Contact staff writer Kristin E. Holmes at 610-313-8211 or email@example.com.