After saving his clan from saber-toothed tigers, Lug the caveboy has become a hero. The only problem: between the nightmares and his sudden skittishness around animals, he doesn't feel like much of a hero. But now he and his friends, Stony and Echo, have even bigger problems. A giant glacier is rolling toward their village—faster than any ordinary mass of ice should move—and it's on course to crush the whole settlement! Maybe Blast, the mysterious northern boy who lives on the glacier, can help Lug's clan. Or maybe it will be up to Lug to save the day again, whether he's ready to or not.