Even at the end, the secret police thought they would survive. The most feared security service in the Communist bloc, the Ministerium für Staatssicherheit – commonly known as the Stasi – had constructed a surveillance apparatus that penetrated every corner of East German society. With 93,000 employees, it was larger even than the East German army; another 173,000 East Germans collaborated as Stasi informers. The Stasi's surveillance records, stored in its sprawling complex on Normannestrasse in Lichtenberg, a suburb of East Berlin, were massive. Put end-to-end, the shelves of files would have stretched for 120 miles.

An equally massive catalog of index cards, organized within an array of mechanized cabinets and known internally as the F22 index, allowed Stasi workers to access this mass of information. However, the Stasi had taken a precautionary step to ensure the security of the information in its files. Pseudonyms were used in place of the real names of informants and victims, in the files themselves and also in the F22 index. To decode the files – to know who had been spying on whom – a select group of Stasi workers were given access to a second card catalog, the F16 index, which matched pseudonyms to real names. Without the F16 index, the meaning of the files would have been practically impenetrable.

By fall 1989, the East German government was tottering. The communist regimes of Hungary and Poland had already collapsed, and there were growing street protests in East Germany itself.