It's In The Blood (Book 5). It's In The Blood, #5

The Thirst Within: HarvestBook Five of the "It's In The Blood" SeriesThe most dangerous predator is the one you've invited into your home. For decades, the DeClue family has seen Angel as their innocent face-a boy trapped by a curse in a ten-year-old's body. They've protected him, loved him, and trusted him. They never suspected that behind his childlike smile lies the mind of a thirty-nine-year-old predator who has been harvesting from the innocent for years.
Angel's secrets are written in blood. He is the shadow behind the "disappearance" of Lucifer's grandfather, and now, he has set his sights on a new prize: six-year-old Michael Hall. As the town of Craig erupts in a desperate, frantic search for the missing boy, the DeClues are hunting a monster they believe is a stranger. They have no idea that the killer is sleeping in the room next door, plotting to turn Michael into a creature of the night by any means necessary.
While Officer Tommy Russle follows a trail of shadows that even his E. S. P. can't fully explain, the ancient evil of Miguel Sanchez finds a new, perfect protégé in Angel. In a house built on loyalty, the ultimate betrayal is unfolding-and this time, the harvest has only just begun.