Second Death(The Second Series 1) by Emily Reese

When Meghan Monroe went missing, her twin brother Mike swore to find her. The harder he looked, the less he seemed to find until he came across a book called The Collector. If his hunch is correct, his professor, Claire Wallace, holds the key to finding his sister. But no one knows better than Claire that finding Meghan might be the least of Mikes worries. After he ignore