The end of World War II means the beginning of the Cold War. Former allies US and USSR have fallen out, and as a consequence, Germany is divided into two different states: West Germany, a federal republic and democracy, occupied by the US, UK and France. And East Germany, a socialist state with a one party system, occupied by the USSR. The border runs right through the heart of the country, dividing friends and families. East Germany surrounds itself by a fence, and in 1961, the Berlin Wall is erected, cutting off the last means of escape. The opposing systems watch each other with mistrust, and heavily arm themselves with high end weapons. And they spy on each other as best they can. This West German TV series is based on real cases of German-German espionage of the time. There is no regular cast, although a lot of actors appear in several episodes, taking on different roles. Each story is told differently and set in different locations, depending on the plot. The point of view changes, too - some episodes are told from the perspective of the spy, some form the perspective of the police or West German intelligence (Bundesnachrichtendienst, Militärischer Abschirmdienst), some center around Stasi officials. In many episodes, people in key positions are drawn unwillingly into espionage with the threat that their relatives in East Germany would suffer the consequences if they did't comply. Since this is a West German series, and based on cases that have been discovered by their intelligence, their side always wins in the end. Nevertheless, it's not a simple good guys versus bad guys structure. The motives and struggles of both sides are taken seriously, and viewers can make up their own mind about what's right or wrong.
—emkarpf
