The Redcastle Redemption - The Athena Effect, #4

Things finally seem peaceful for Cali and Calvin, but the twins are still struggling with their new-found freedom. Layla senses that more trouble still lurks in her future, while Michael's happiness is being crushed under the weight of a terrible secret. When someone new discovers the girl's special talents, he will stop at nothing to put them to use. The cousins must face their most brutal adversary yet, and everyone is forced to fight for both their lives and their loves.