About 20,000 years before our era, a strange animal unexpectedly triggers a new ice age. While the animals, panic-stricken, flee the ice winds, Manny, a solitary mammoth, goes against the grain. He is soon flanked by a companion, Sid the sloth, who has imposed his loquacious presence. On their way, the two companions cross paths with a human tribe decimated by the merciless saber-toothed tigers.