The Final Church

From publisher blurb: Over the last half-century, the Hoffmann Institute has become increasingly aware of the existence of the Final Church. At first, they only recognized that various cults had nebulous connections. Then, they realized that some cults were subordinate to others. Finally, the Institute’s analysts theorized that there might be a single "master" cult. The Institute decided to try to infiltrate this cult, but the progress has been glacially slow. Some Hoffmann deep cover agents have turned up dead. Others have simply vanished, eventually declared dead by the Institute. Contact with remaining agents is rare for security reasons, and the Institute uses a series of codes to keep their personnel files from falling into the wrong hands.