Kiss Her Goodbye by Lisa Gardner

Recent Afghan refugee and young mother Sabera Ahmadi was last seen exiting her place of work three weeks ago. The local police have yet to open a case, while her older, domineering husband seems unconcerned. At the insistence of Sabera’s closest friend, missing persons expert Frankie Elkin agrees to take up the search just in time for a video of Sabera to surface—showing her walking away from the scene of a brutal double murder.
Frankie quickly notes there’s much more to the Ahmadi family than meets the eye. The father Isaad is a brilliant mathematician, Sabera a gifted linguist, and their little girl Zahra has an uncanny ability to remember anything she sees. Which given everything that has happened during the girl’s short life, may be a terrible curse.
When Isaad also disappears under mysterious circumstances and an attempt is made on Zahra’s life, Frankie realizes she must crack the code of this family’s horrific past. Someone is coming for the Ahmadis. And violence is clearly an option.

When everything is on the line, how far would you go to protect the ones you love? Frankie is about to find out.