Serge and Beate Klarsfeld have dedicated their lives to tracking down Nazis

Their story reads like a spy novel and includes international schemes, jail time, and assumed identities

Beate Klarsfeld, who once slapped a German Chancellor in the face, is now being awarded one of France's top honors.

In 1968, Beate Klarsfeld jumped up during a political rally and slapped German Chancellor Georg Kiesinger in the face.

On Monday, the 79-year-old received one of France's top awards, the National Order of Merit. In the same ceremony, her husband Serge Klarsfeld, 83, received the highest national award, the Grand Cross of the Legion of Honor. The couple were recognized by French President Emmanuel Macron for their lifelong dedication to tracking and exposing war criminals.

The Klarsfelds call it their family business. Their enterprise: hunting Nazis. And they're good at what they do.

Chancellor Kiesinger, who worked in the Nazi's radio propaganda arm under Joseph Goebbels, was never charged with war crimes. But the couple — who focus on higher-level Nazis, many of whom fled Germany after the war — has helped bring to justice at least 10 war criminals.

The only known photograph of Klaus Barbie in uniform. The "Butcher of Lyon" was responsible for the arrest, torture, and death of thousands of people in France during World War II. He was finally arrested in Bolivia in 1983 after the Karsfelds tracked him down. AP Photo

Notorious Gestapo officer Klaus Barbie, nicknamed the "Butcher of Lyon," was arrested in Bolivia in 1983. Beate Klarsfeld had tracked him down there over a decade earlier. Barbie was responsible for a reign of terror in France during World War II, and for the arrest and torture or death of tens of thousands of people during that time, including the deportation of 44 Jewish children from the village of Izeu.

The Klarsfelds specialize in tracking down Nazis who found their way out of Germany after the war. They campaigned for the arrest of both Walter Rauff and Alois Brunner. Rauff, who invented the mobile gas chamber while working under Reinhard Heydrich, ultimately made his way to Chile, where he died before he could be extradited and tried. Klarsfeld claims she traced Brunner to Syria, where he reportedly died years ago. Brunner served as the assistant to Adolf Eichmann — the architect of Hitler's "Final Solution" — and is responsible for sending tens of thousands of Jews to concentration camps.

Serge Klarsfeld has previously been awarded with a lower rank of the Legion of Honor. Their son Arno, who is named after Serge's father, a victim of murder at Auschwitz, now helps them prosecute some of the Nazis they track down.