Cragbridge Hall: The Avatar Battle by Chad Morris

Cragbridge Hall: The Avatar Battle by Chad Morris is the second book in the series. Abby and Derick are continuing their education at Cragbridge Hall, but things are not smooth sailing.

One by one, adults at the school whom Grandpa has entrusted with his secret of time travel, and with the keys to the bridge that enable that, are ending up in comas, with their keys stolen! The enemy wants to change the past and have control over time, but will the twins be able to stop him in time? And what will they do when their parents and grandpa are trapped on the Hindenburg with minutes to go before it crashes in a fireball? Will they rescue their family in time?