The German battle cruiser SMS Blücher is sunk by British forces, and Otto Kuehn is taken as a prisoner of war.

Otto and Leopold attend a Hitler rally in Kiel, and Otto joins the Nazi Party the following day.

Otto loans his rival Reinhard Heydrich 100 marks for a train ticket, and Heydrich wins the coveted SS intelligence job over Otto.

Leopold brings Ruth to a Joseph Goebbels gala in Berlin, where she meets Goebbels and begins an affair with him.

Goebbels discovers Ruth's half-Jewish heritage and arranges for the Kuehn family to spy for Japan in Hawaii.

Otto signs a lucrative spy contract with a Japanese naval attaché in Berlin, earning $2,000 a month.

The Kuehn family settles in Hawaii and begins gathering intelligence by hosting lavish parties for US military officers.

The FBI opens a permanent Honolulu field office under Special Agent Robert Shivers and begins investigating the Kuehn family.

Japanese intelligence officer Yoshikawa visits the Kuehn home, delivers $14,000 in cash, and activates Otto for the final Pearl Harbor mission.

Otto drives to the Japanese consulate with Friedel as cover and delivers a simplified naval signaling plan.

Japan launches a devastating attack on Pearl Harbor, destroying much of the US Pacific Fleet in 90 minutes.

FBI agents arrest Otto, Friedel, and fifteen-year-old Eberhard at their home shortly after midnight on December 8.

After hours of interrogation without food or water, Otto breaks down and signs a full confession.

The military commission deliberates for eleven minutes and sentences Otto to death by firing squad.

A Supreme Court ruling on a separate espionage case leads to Otto's death sentence being commuted to 50 years of hard labor.

After surviving a World War I naval battle as a prisoner of war, Otto Kuehn reinvents himself as a Nazi Party member who catches the attention of German propaganda chief Joseph Goebbels. When Goebbels needs to quietly remove his half-Jewish mistress Ruth from Berlin, he arranges for the Kuehn family to relocate to Hawaii as paid spies for Japan. The family establishes cover stories, cultivates military contacts, and delivers intelligence that helps Japan plan its attack on Pearl Harbor. On December 7, 1941, Japan strikes, and the FBI immediately arrests the Kuehn family using evidence recovered from the Japanese consulate. Otto is convicted by a secret military tribunal and sentenced to death, but a Supreme Court ruling on a separate espionage case ultimately saves his life and his sentence is commuted to decades of hard labor.

The headline events of the Kuehn family's Nazi spy operation and its consequences.

Ruth and her younger brother Hans burn five boxes of Kuehn family records in a field in Germany.

Otto marries Friedel Birk and legally adopts her two children from previous relationships, Leopold and Ruth.

Ruth joins the Nazi girls' youth organization and Leopold enlists in the SA Brownshirts, immersing the family in Nazi ideology.

A Nazi official named Schmidt arranges Otto's arrest and planned roadside execution; Friedel secures his release just in time.

Otto travels to Shanghai and meets Japanese intelligence contact Captain Kanji Ogawa, who deposits $20,000 in the Kuehns' account.

Ruth guides a disguised Japanese naval intelligence officer on a detailed tour of Oahu's military installations, including Pearl Harbor.

Friedel travels to Japan, discovers Ruth's fiancé Homberg with another woman, demands payment, and forces Ruth to break off the engagement.

Friedel and Ruth open the Kailua Beauty Shop to gather intelligence from the wives of US Navy officers.

Otto builds a dormer window onto the Kuehn house in Kalama, immediately drawing FBI suspicion that it is meant for signaling.

Double agent Dusko Popov presents FBI Director Hoover with microdot orders detailing German interest in Pearl Harbor's defenses, but Hoover dismisses the warning.

The USS Arizona explodes catastrophically during the Pearl Harbor attack, killing approximately 1,500 men.

FBI agents storm the Japanese consulate and recover partially burned documents, including the telegram detailing Otto's signal plan.

Fifteen-year-old Eberhard and nine-year-old Hans are called to testify against their father at the secret military tribunal.

Eberhard is released from the internment camp after five months and renounces his family's Nazi ideology.

Friedel, Ruth, and Hans are repatriated to Germany in a prisoner exchange while Eberhard fights in the Battle of Okinawa.

The story opens with Ruth and Hans burning five boxes of family records in a field in Germany, a desperate act of concealment that frames the entire narrative. The Kuehn family immerses itself in Nazi organizations through its youth groups and party structures, but a rival official's revenge plot nearly gets Otto executed before Friedel stages a daring last-minute rescue. Once in Hawaii, Ruth and Friedel run active intelligence operations, from guiding disguised Japanese officers around Oahu's military bases to running a beauty shop designed to target naval officers' wives. A crucial warning about the impending attack is brought to FBI Director Hoover by double agent Dusko Popov but is dismissed outright, and the attack proceeds on schedule. In the chaotic aftermath, FBI agents recover damning evidence from the Japanese consulate, the family's young sons are compelled to testify against their father, and the family members are separated and dispersed across internment camps before being ultimately scattered to different continents.

The cover operations, family dynamics, and supporting figures that sustained the spy ring.

Christine meets her Aunt Ruth, who grows agitated when asked about the family and warns Christine not to investigate the past.

Christine and her husband Mark find Otto Kuehn listed as a Nazi spy in multiple Pearl Harbor history books at a bookstore.

Christine confronts her father Eberhard, who initially denies the accusations but calls back sobbing and confirms the family's dark history.

Penniless after World War I, Otto unexpectedly receives a large inheritance from his Aunt Elsa, which he quickly loses on failed business ventures.

During the Night of the Long Knives, Otto accepts a bribe of 30,000 marks to spare an assassination target, leaving himself dangerously compromised.

Christine discovers through research that Ruth's biological father was Jewish architect Martin Punitzer, making Ruth half-Jewish.

Fifteen-year-old Eberhard voices his hatred of the Nazis to a friend, prompting Friedel to restrict his socializing to protect the family's cover.

On the evening before the attack, Yoshikawa conducts a final reconnaissance and transmits detailed ship positions to the approaching Japanese fleet.

After the attack, FBI agents decode a telegram detailing Otto's signal plan and identify the Kalama dormer window as a unique landmark.

Ruth's husband Jacob Moore tells FBI agents that he has long suspected his wife and is relieved by her arrest.

Hidden FBI microphones record Otto telling Friedel that he signed a full confession, as both weep fearing execution at dawn.

German saboteur George Dasch surrenders to the FBI, triggering a Supreme Court espionage case that will ultimately determine Otto's fate.

Eberhard writes Ruth a letter declaring he will never be German again and explicitly condemning the Nazis and Japanese imperialists.

Eberhard meets his frail, aging father Otto one last time at a New York coffee shop and refuses his plea to return to Germany.

Christine witnesses antisemitic incidents in her Maryland neighborhood and resolves to write Family of Spies rather than protect her family's secret.

Christine Kuehn's investigation begins when she encounters her Aunt Ruth and later receives a screenwriter's letter that forces her to confront evidence of her grandfather's spy activities, shattering everything her father told her about his past. Tracing the family history back through Otto's financial failures and embrace of extremist ideology, she uncovers the specific turning points that sent them on a path toward espionage and treason. She discovers that Ruth's secret Jewish ancestry was the hidden catalyst for the entire Hawaii mission, as Goebbels needed to erase a potential scandal before the Nuremberg Laws could destroy him. On the eve of the Pearl Harbor attack, key evidence arrives too late to prevent catastrophe, and in the aftermath, the FBI uncovers the physical proof needed to build an airtight case against the family. After the war, Eberhard makes a definitive break from his family's ideology that his father never forgives, and Christine ultimately decides to publish the hidden history after witnessing the reemergence of the same hateful forces her grandparents once served.

The discoveries, decisions, and emotional breaks that shaped the family's fate and the author's decades-long investigation.