South America is a land time forgot, with giant birds, the last of a trunked, hoofed herbivore, huge sloths, and giant armadillos. But the isolation of this continent has ended; and land bridge now connects South America with North America. With it has come a new species of predator; Smilodon, the infamous saber-toothed ""tiger"".

But life here is no easier for the largest of all cats, especially for Half Tooth, a large male Smilodon. Having been usurped by two other males for breeding rights with a clan of females, Half Tooth struggles to survive on his own, a daunting prospect that claims many a lone male's life. But fate has a different agenda in store for Half Tooth.