Sid, a talkative sloth is left behind sleeping while everyone else begins the journey to the south. After waking up, he meets Manny, a mammoth who travels to the north, and decides to join him. On the way, they rescue a baby whose mom takes him and jump into a river to escape an attack. They decide to find his father to return the baby to him. Diego, one of the tigers that attacked the humans, comes also claiming the baby.