Two years after the events of the
second film,
Dave Seville,
the Chipmunks, and
the Chipettes embark on a cruise to attend the International Music Awards. While aboard, Alvin causes mischief by encouraging a water gun fight in the adult section of the ship, prompting Dave to apologize to the captain over dinner. Disobeying Dave's instructions, the Chipettes sneak into the ship's dance club while Alvin and Simon head to the casino. Dave discovers his former supervisor
Ian Hawke works as the ship's safety officer dressed as a pelican; Ian sets to inform the captain if the Chipmunks and Chipettes cause further trouble. After catching them in the act, Dave warns them of missing the International Music Awards. The next day, Alvin goes
parasailing on a kite with the others attached, but strong winds carry them away into the
Pacific Ocean. Dave attempts to use a
hang-glider to find them but is stopped by Ian, causing both to also be stranded at sea. The Chipmunks find a deserted island where they meet a castaway named Zoe. At her treehouse, Eleanor injures her ankle and Simon is bitten by a spider; its venom results in a drastic personality shift, causing Simon to believe he is a French adventurer named "Simone". Later, Zoe takes "Simone", Jeanette, Eleanor, and Theodore to a lake, where "Simone" discovers a cave hidden behind a waterfall and retrieves a gold bracelet, which he gives to Jeanette. Meanwhile, Dave enlists Ian's help to find the same island and rescue the Chipmunks. The next day, Brittany and Alvin spot the island's active volcano, prompting the Chipmunks to prepare a raft to evacuate. While Jeanette and "Simone" look for food, "Simone" is knocked unconscious and Jeanette is abducted; upon waking, Simon returns to his original personality with no recollection of the events after the bite. The Chipmunks discover that Zoe has taken Jeanette and head towards the waterfall, where Dave and Alvin witness Zoe forcing Jeanette to retrieve treasure in the cave while tied to a rope. Zoe reveals that she originally came to the island seeking the treasure, but her decade of isolation caused
memory loss and an unhealthy obsession for her search. As the volcano begins to erupt, Zoe accidentally releases the rope and Jeanette runs with Dave and Alvin to the raft. At a log crossing, Zoe tries to recapture Jeanette with the rope until Alvin cuts it with a
Swiss Army knife previously confiscated by Dave. However, the log collapses, leaving Dave hanging from a branch and prompting Alvin and a reformed Ian to convince Zoe to help save him. The group escapes the eruption and safely boards the raft. Stranded once again, Jeanette forgives Zoe and gives her the gold bracelet that Simon had earlier retrieved. Alvin also apologizes to Dave for his antics on the ship, and the group is eventually rescued. The Chipmunks and Chipettes perform at the International Music Awards. Ian begins a new screenwriting career by selling a screenplay about Zoe's story to Hollywood, finally restoring his fortune and making Zoe famous. On the flight home to
Los Angeles, Alvin plays a prank on the passengers by announcing they are en route to
Timbuktu, much to Dave's annoyance. ==Cast==