The Jade Butterfly by Jeffrey Round

A seemingly casual encounter in a downtown bar sends missing persons investigator Dan Sharp in search of a woman presumed dead in the Tiananmen Square Massacre. Twenty years after her disappearance, her brother hopes to find a woman he glimpsed on the Internet and believes to be his sister, now living in Toronto. The closer Dan gets to finding her, however, the less things make sense. Just when he thinks he know what's driving his client, an unexpected revelation forces him to choose between what he's been told and his gut instinct that says things are not all they seem.