The second perimeter
(Book)

When the Secretary of the Navy's nephew says he believes that two colleagues at a U.S. naval base may be committing fraud, his uncle is skeptical. Reluctant to launch an official investigation based on vague suspicions, the Secretary asks the Speaker of the House to send his troubleshooter, Joe DeMarco, to check out the story. As DeMarco and his friend Emma, a retired DIA agent, began to investigate what they thought was a low-stakes swindle, they realize that an espionage ring has infiltrated the naval base. The leader of the cell is a woman with whom Emma has a history and who cares about only one thing: destroying Emma. DeMarco has never been near a spy in his life, and now he's dealing with a foreign agent more deadly than anyone he's ever encountered.--From publisher description.