To avoid a really bad frostbite, Earth's majestic creatures begin migrating south. The exceptions are a woolly mammoth named Manfred, and a lazy sloth named Sid. When Sid "adopts" Manfred as his protector, the mammoth tries everything he can to unload his new found baggage. Manny is roped by Sid into helping reunite an abandoned human baby named Roshan with his family. They are joined by Diego, a saber-toothed tiger who befriends Sid and Manny, all the while seeing the infant as a tasty treat.