When a deadly diphtheria epidemic swept through Nome, Alaska, in 1925, the local doctor knew that without a fresh batch of antitoxin, his patients would die. The lifesaving serum was a thousand miles away, the port was icebound, and planes couldn't fly in blizzard conditions—only the dogs could make it. The heroic dash of dog teams across the Alaskan wilderness to Nome inspired the annual Iditarod Trail Sled Dog Race and immortalized Balto, the lead dog of the last team whose bronze statue still stands in New York City's Central Park. This is the greatest dog story, never fully told until now.