In 1957, the Federal Intelligence Service began listening in on mysterious numbered radio stations from the East. But it was not until the spring of 1973 that these mysterious messages revealed a controversial suspicion. Congratulations on the birth of a son led to a man in the Chancellery. Günter Guillaume, Willy Brandt's advisor, was targeted as a GDR spy. The Office for the Protection of the Constitution raised the alarm - and what began as routine surveillance soon developed into a real scandal.

The young Günter Guillaume survives the World War as one of the few in his class and returns to his hometown of Berlin. At the same time, Willy Brandt returns to Germany from exile in 1945. Both strive for a new beginning in the rubble and campaign for a new, better Germany. But in the East there is discontent among the population and hundreds of thousands flee to the West. This gives the state security the opportunity to infiltrate spies, including Günter Guillaume, who soon makes a career.

In 1972, a power struggle rocked the Federal Republic of Germany, triggered by the Chancellor's new Eastern policy and increasing anger from the opposition. New elections were imminent. Guillaume was also part of Brandt's election campaign team. For six weeks, Guillaume accompanied Brandt on the "Vote for Willy" tour in a special train, made up to eight appearances a day, slept too little, smoked and drank too much. Despite the strain, he remained in office as Chancellor.

In April 1974, the bomb explodes and the spy in the Chancellery is exposed. Brandt comes under pressure. The GDR government panics because the fall of the Chancellor could be fatal for the relationship between the two German states. And then Brandt's private life comes into focus. An explosive list emerges: names of supposed lovers. The hunt is on. The boundaries between political intrigue and personal drama become blurred.