Back one million years ago, South America was a continent of exotic oversized creatures found nowhere else on Earth - huge terror birds, giant ground sloths and spiky-tailed relatives of the armadillo as big as cars. The deadliest animal of them all was smilodon, the largest of the sabre-tooth cats, with canines like carving knives. The programme follows the fortunes of an individual male, Half Tooth. Ousted from his clan by a pair of rival males, his life suddenly becomes a struggle to survive in this alien world.