What is the main conflict in A String in the Harp by Nancy Bond?

Jen and Peter Morgan must not only face the fracturing of their family after their mother’s death but a reality in which magic bound to an old harp tuning key is summoning the past of welsh bard Taliesin to their lives. Beset by visions summoned to the real world and greedy academic Dr. Owen they must find the grave of Taliesin to return the key in hopes of returning the world to normal and find a way to heal the rifts in their family.