The Hostage Room by Lynne Heitman
She left the corporate world of airlines, lured by the dark arts of private investigation. Now Alex Shanahan is stirring up a cold case with global implications. Years after she dumped him for a younger man, the scheming ex-wife of Alex's partner, Harvey Baltimore, returns for an unexpected visit. While Alex tries to figure out why Rachael is back, another mystery begins to unfold halfway around the world. Four years after a bloody, high- profile airline hijacking, personal effects belonging to the victims are found in a terrorist safe house. The discovery of this chilling time capsule triggers a chain reaction that leads straight back to Rachael. By the time Alex has untangled Rachael's lies, she will be on the run from the Russian Mafia, caught in the web of a global vigilante group, and forced to take a reluctant trip into her partner's past - a painful, and often perilous, trip...