In one of the earth's most amazing migrations, more than 100,000 caribou trek thousands of miles each year over high mountain ranges, through snowy passes, and across icy rivers. But they have to battle more than just the brutal elements. Hungry wolves, huge grizzly bears, human hunters, and hordes of bloodthirsty insects besiege the herd as it travels to its one safe haven--Alaska's Arctic National Wildlife Refuge. There, those that survive the trip...