The Twelfth Card by Jeffrey Deaver

Geneva Settle is a bright young high school student from Harlem writing a paper about one of her ancestors, a former slave called Charles Singleton. Geneva is also the target of a ruthless professional killer. Criminalist Lincoln Rhyme and his policewoman partner Amelia Sachs are called into the case, working frantically to anticipate where the hired gun will strike next and how to stop him, all the while trying to get to the truth of Charles Singleton, and the reason that Geneva has been targeted.