De Castrique, Mark. Secret lives mystery (Series)

"For seventy-five-year-old former FBI agent Ethel Fiona Crestwater, her age is nothing but an advantage when it comes to ferreting out secrets. Who's going to notice the little old woman in the corner? Besides, Ethel might be officially retired, but she knows everyone in DC law enforcement--and is smarter than all of them combined. When a former colleague asks Ethel for help, she agrees without a second thought. But the favor throws Ethel back eighteen years, to the botched sting operation that resulted in the murder of an innocent young woman by a Russian gangster--and nearly ended Ethel's own life too. Soon, Ethel and her young tech-whizz sidekick Jesse, her double-first-cousin-twice-removed , find themselves in the crosshairs of some very bad--and very desperate--men who'll do anything to get their hands on the state secrets they're seeking. Ethel will have to use all the skills she's learned during her long career if she's to save the day, and keep both herself and her beloved cousin alive"--