Back when the Earth was being overrun by glaciers, and animals were scurrying to save themselves from the upcoming Ice Age, a stupid sloth named Sid, a woolly mammoth named Manny, a saber-toothed tiger named Diego, and an acorn-loving saber-toothed squirrel named Scrat are forced to become unlikely heroes. The four reluctantly come together when they have to return a human child to its father while braving the deadly elements of the impending Ice Age.