Scrat's nutty pursuit of the cursed acorn, which he's been after since the dawn of time, has world-changing consequences -- a continental cataclysm that triggers the greatest adventure of all for Manny, Diego and Sid. In the wake of these upheavals, Sid reunites with his cantankerous Granny, and the herd encounters a ragtag menagerie of seafaring pirates determined to stop them from returning home.