The Expatriates by Janice Lee

 Margaret is an American wife who packs up her family and moves them to Hong Kong when her husband's job calls for it. She and her three kids are getting accustomed to life overseas when Margaret hires a Korean-American 20-something named Mercy to be a mother's helper for her kids. On a family trip to Korea, the youngest child, a boy just called G, vanishes while Margaret is in the bathroom and Mercy is supposed to be watching the kids. Even after her husband and other kids have to return to Hong Kong, Margaret stays in Korea trying to find her son. At the same time, Mercy decides she'd better get out of the picture and goes back to her directionless life in Hong Kong. The third main character is another expat called Hillary, married to David. They have been trying unsuccessfully to have a baby and David is losing interest in the marriage. Since Hong Kong is really like a small village where everyone knows everyone else, David and Mercy cross paths, which takes the story in a whole other direction. I thought it was a very good story with well-developed characters, though I'm not sure I'm buying the ending.

I really did not like the character of Mercy, who was like a giant wrecking ball to 2 different ex-pat families and who totally wasted the time of a nice guy who was interested in dating her. Then her mother comes and rescues her after she finds herself in another pickle. It didn't seem like she was ever going to really grow up and take responsibility for her actions. Which is part of the reason why I didn't like the ending.

The Piano Teacher by the same author was also a good read.