Bad Company by Sara Paretsky

The CIA forced Lily to retire before she was ready. She’d spent forty years as a field agent. She’d been skilled, resourceful, dedicated – everything that makes a good agent, but she’d rubbed too many of her bosses the wrong way. They jumped on a botched op as an excuse to fire her. Now in her seventies, waiting in a doctor’s office, she reads a magazine article that startles her out of retirement.

The story casts doubt on everything she believed about her first – and happiest – posting in Hayalistan, one of the old Soviet republics. Lily’s angry, and she decides to find out what really happened when she was stationed there. As word of her investigation gets back to the CIA, the Company knows they must silence her. But Lily’s aging body can’t perform the feats it managed in her forties and fifties, and escaping their attempts on her life will test her physical and mental skills at a whole new level.