On a routine intelligence gathering mission in Tehran, Jack Ryan, Jr., has lunch with his oldest friend, Seth Gregory, an engineer overseeing a transcontinental railway project. As they part, Seth slips Jack a key, along with a perplexing message. The next day Jack is summoned to an apartment where two men claim Seth has disappeared-- gone to ground with funds for a vital intelligence operation. They leave Jack with a warning: If you hear from Seth Gregory, call us immediately. And do not get involved. But they don't know Jack....