Tom Clancy Under Fire (Jack Ryan Jr. Series #2)

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 gives 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.  Jack’s oldest friend has turned, they insist.

They leave Jack with a warning:  If you h…