Playing around while aboard a cruise ship, the Chipmunks and Chipettes accidentally go overboard and end up marooned in a tropical paradise. They discover their new turf is not as deserted as it seems.
Lex Luthor enacts his plan to rid the world of Superman, once and for all. Succeeding with solar radiation poisoning, the Man of Steel is slowly dying. With what little times remains, the Last Son of Krypton must confront the revealing of his secret identity to Lois Lane and face Luthor in a final battle.
Through a series of misunderstandings, Alvin, Simon and Theodore come to believe that Dave is going to propose to his new girlfriend in New York City - and dump them. They have three days to get to him and stop the proposal.