In this unmemorable thriller from Mitchell (State of Lies), the life of Whitney Garrison, a law school graduate busy cramming for the bar exam, is upended after she finds the body of a man who was shot in the head outside the Arlington, Va., coffee shop where she works as a barista. Whitney spots someone with a gun on the shop's roof, but because she has face blindness, a condition that makes it hard for her to remember faces, she can't describe the gunman with any accuracy to the police. Whitney is able to identify the victim as a regular customer, Joe, based on the cops' discovery of a coffee cup near the corpse with a label fitting Joe's unique routine order. Whitney later becomes a target, even as she develops an improbable romantic attachment to the detective investigating the murder, which she suspects may have far-reaching implications connected to her previous work on Capitol Hill. Thin characterizations are matched by an implausible payoff. Readers who like to see good people triumph over adversity will best appreciate this one. Agent: Natasha Kern, Natasha Kern Agency. (Oct.)