Cross my Heart (Alex Cross Book 21) by James Patterson

The stakes are higher than ever for Alex Cross as he faces his most personal enemy yet: a criminal who threatens his family. Detective Alex Cross is a family man at heart: nothing matters more to him than his children, his grandmother, and his wife Bree. His love of his family is his anchor, and gives him the strength to confront evil in his work. One man knows this deeply, and uses Alex's strength as a weapon against him in the most unsettling and unexpected novel of James Patterson's career. When the ones Cross loves are in danger, he will do anything to protect them. But if he does anything to protect them, they will die. Cross My Heart is the most powerful Alex Cross novel ever, propelled by the ever-ingenious mind of James Patterson, the world's #1 bestselling writer.