Book Description: Nadia and Aidan Shaw, 13-year-old twins from Cold Spring, New York stumble upon a magical black Celtic stone, the Ravenstone. It pulses with the light of shamanic power and is a vehicle for time travel! In this, the second novel in the Ravenstone series, the twins experience a terrifyingly real vision of a massive earthquake which threatens their mother's life. The mission to save her grows in scope as they investigate, and their subsequent trips across time and space force them to face unimaginable dangers. They must rely on their growing skills and all the powerful magic of the Ravenstone in their urgent need