A Double Life by Flynn Berry

Her mother was attacked and her nanny brutally killed by her dad when she was very young but Claire still struggles with the hope that he is not a monster. Now she must live in fear again because he has been sighted once again after vanishing after the murder. She wants to believe that he had a reason for doing what he did even though she knows he must be a cold-hearted killer plus she is trying to help her younger brother manage his addiction and get him back into rehab. Instead of constantly living in fear she decides to try to find and confront her dad herself so she can put the past to rest. This could prove to be a huge mistake. Suspenseful and heartbreaking.