While the saber-toothed squirrel Skrat still tries in vain to retrieve his precious acorns. The three awkward trios of Mammoth Manny, Lazy Sid. And the saber-toothed tiger Diego are already in an isolated valley with many other animals. However, the trio discovered that the ice wall around the valley could hardly stop the large amount of water behind it. And its molten state could break apart and flood the valley.
Since their only chance of survival was in a boat at the other end of the valley, the three of them followed the desperate fugitive there. Along the way, they met Ellie, a female mammoth, who was convinced that she was a possum like her siblings. As these strange people continue on their way, they must learn to get along, even if Manny tries to find a connection with this strange woman, she may be the only other of her kind.