Cragbridge Hall, Book 2: the Avatar Battle

In book 2 of this trilogy, Abby and Derick begin their second semester at Cragbridge Hall, the most prestigious secondary school in the world. But when Grandpa Cragbridge admits them to the Council of Keys-a secret group of people who have keys to travel back in time-strange things begin to happen. One by one, members are found unconscious and unable to wake, their keys stolen. Now Abby and Derick must scramble to figure out who is behind the attacks before they become the next victims, which would give their enemy the power to change the past forever.