Phantom instinct : a novel / Meg Gardiner.

"When shots ring out in a crowded L.A. club, bartender Harper Flynn watches helplessly as her boyfriend, Drew, is gunned down in the cross fire. Then somebody throws a Molotov cocktail, and the club is quickly engulfed in flames. L.A. Sheriff Deputy Aiden Garrison sees a gunman in a hoodie and gas mask taking aim at Harper, but before he can help her a wall collapses, bringing the building down and badly injuring him. A year later, Harper is trying to rebuild her life. She has quit her job and gone back to college. Meanwhile, the investigation into the shoot-out has been closed. The two gunmen were killed when the building collapsed. Certain that a third gunman escaped and is targeting the survivors, Harper enlists the help of Aiden Garrison, the only person willing to listen. But the traumatic brain injury he suffered has cut his career short and left him with Fregoli syndrome, a rare type of face blindness that causes the delusion that random people are actually a single person changing disguises. As Harper and Aiden delve into the case, Harper realizes that her presence during the attack was no coincidence--and that her only ally is unstable, mistrustful of her, and seeing the same enemy everywhere he looks" -- from publisher's web site.