The examination of past and present fierce predators begins with a search for the legendary Australian sea serpent, which may actually be one and the same as the ferocious Australian tiger snake.

A visit to Costa Rica spotlights the six-inch Brazilian wandering spider, which is one of the world's deadliest spider species.

The giant snakehead fish, a territorial predator that's native to eastern Asia, is featured via trips to Thailand and Arkansas, where it has infested a river.

A search for jaguars in the Yucatan Peninsula.

Deadly crocodile attacks along the Limpopo River in South Africa are investigated.

Over 2,200 Gray Wolves are estimated to roam the forests of northern Minnesota; several fatal attacks have been the result of the wolves acting against their instincts.

Sean is in Australia, tracking down a legendary beast, the Megalania; the Megalania is a gigantic ancient reptile that is rumored to still live in the remote microclimates of Australia's Greater Blue Mountains.

Although hunted into extinction nearly a century ago, recent sightings suggest that the ferocious Eastern Cougar has resurfaced in the United States.