A saber-toothed squirrel known as Scrat attempts to find a place to store his single acorn. Eventually, as he tries to stomp it into the ground, he causes a large crack in the ground that extends for miles before setting off a large avalanche which nearly crushes him. He barely escapes, but finds himself stepped on by a herd of prehistoric animals migrating south in order to escape the forthcoming ice age. Sid, a clumsy ground sloth, is left behind by his family and decides to move on by himself but is attacked by two prehistoric rhinos whom he angered by ruining their meal. Sid is soon saved by Manny, an agitated woolly mammoth heading north, who fights the rhinos off and continues his path. Not wanting to be alone and unprotected, Sid follows Manny. Meanwhile, Soto, the leader of a pack of saber-toothed tigers, wants revenge on a group of humans for killing half of his pack, by eating the chief's infant son,<ref name="Strong Official"></ref> alive. Soto leads a raid on the human camp, during which the baby's mother is separated from everyone else and jumps down a waterfall upon being cornered by Soto's lieutenant, Diego (Ice Age). As punishment for his failure, Diego is sent to find and retrieve the baby.