In a Bolivian jungle, Adam and Caveman Rob pursue the fabled Executioner Wasp, Warrior Wasp, and Goliath Bird-Eating Tarantula. One causes a medical emergency, and another delivers a nightmarish bite that leaves Adam's arm partially paralyzed.

Adam and Caveman Rob head to South Africa to face the giant Bark Scorpion, the tiny Uroplectes Scorpion, and the highly venomous Lion Fish. Big pain comes in small packages, and the effects of marine animals' toxins are truly the next level of pain.

In Africa, Adam and Caveman Rob search for the Nile Monitor Lizard and the Velvet Ant but are attacked by an even deadlier animal and are lucky to escape with their lives. The guys experience a brutal bite that makes them question their mission.

In Africa, Adam and Caveman Rob search for the Nile Monitor Lizard and the Velvet Ant but are attacked by an even deadlier animal and are lucky to escape with their lives.

An underwater hunt for the possibly deadly scorpionfish in the Baja, ocean leads to a toxic sting that puts Adam in danger and matches the highest pain score to date, while the Toe biter results in the weirdest pain profile yet.

A wildlife biologist and professional animal handler get bitten and stung by some of the most dangerous animals and vicious stinging insects in the world in an attempt to create a complete and comprehensive pain index that will ultimately help save lives.

The guys encounter two legendary creatures of the Amazon: the Bullet Ant and the Piranha. After hours of pain from the Bullet Ant, Caveman Rob dips his blood covered arm in a tank of Piranhas. What follows is a bloody and painful mess.

Adam and Caveman Rob wrap up the season in Indonesia, with the two worst bites to date, from a Giant Asian Centipede and a 16-foot Reticulated Python. Vomiting, stitches and rivers of blood make them ask if they are able to continue their research.

The crew finds out that the swamp may be manmade.