Gut Instinct by Barb Han

FBI agent Luke Campbell has never been more determined to catch the serial killer who's eluded him for two years. Because this time the monster is after Julie, the ex he walked out on when he returned from Iraq, emotionally scarred and burdened by a secret. Now Luke will do anything — even risk his life — to protect Julie and regain her trust. But it's a tense race against time. Defying FBI rules, Luke keeps Julie by his side throughout a harrowing chase. Finally, at a safe house, it's clear to him that the passion they once shared hasn't cooled. Can Luke redeem himself and keep evil away from the woman he refuses to let go of again?