The second perimeter / Mike Lawson.

Enhanced descriptions from Syndetics:

The dazzling sequel to The Inside Ring finds Joe DeMarco, the Speaker of the House's all-purpose fixer in a battle of wits against a lethal female spy. 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 a relative's vague suspicions, the secretary asks House Speaker, John Mahoney, to send his troubleshooter, 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 government swindle, they come to the terrifying realization that an espionage ring has infiltrated the naval base. The leader of the espionage cell is a woman with whom Emma has a history that goes back to the cold war. Their encounter destroyed the woman's once promising career and turned her into a ruthless operative who cares about only one thing: destroying Emma, the person responsible for her shame, dishonor, and shattered life. DeMarco has never been near a spy in his life--at least not that he knew of--and now he's dealing with a foreign agent who is more deadly than anyone he's ever encountered.