Tunnel Through Time: The Crystal Cave (Volume 2)

Several years after their first adventure, Ari and Seamus are lured into a hidden tunnel by Ari’s Keeshond Ulfur. They are compelled to follow and are then pursued by an ominous black-robed figure. Following a close call at the era-ending Battle of Moira, they are befriended by a Druid who takes them to the far distant past. After learning a perilously powerful secret of the Tuatha Dé Danann and witnessing the origin of the great world civilizations, Ari and Seamus must then return to the time and place of their first trip into the past just in time to try to prevent a tragedy before it is too late.