After the events of "Ice Age: The Meltdown", life changes for Manny and his friends: Scrat is still on the hunt to hold onto his beloved acorn, while finding a possible romance with female saber-toothed squirrel Scratte. Manny and Ellie have become an item and are expecting a baby, which makes Manny anxious to ensure that everything is perfect before their baby arrives. Diego is fed up with being treated like a house-cat and ponders the notion that he is becoming too laid-back. Sid starts to wish for a family of his own and steals some dinosaur eggs, which lands him in a strange underground world where his herd must rescue him while dodging dinosaurs, facing danger left and right, and meeting a one-eyed weasel known as Buck who hunts dinosaurs intently.
