Ever since the earliest missionaries and explorers returned from Africa, stories have been told of strange water-dwelling monsters living in the Congo Basin. The native Pygmy tribes speak of the Mokele-mbembe, an animal with a long, thin neck and a body the size of an elephant that seems to resemble a sauropod dinosaur. Could there be a population of dinosaurs living in the remote jungle? Starting in Cameroon, where there is a history of Mokele-mbembe sightings, Spain will meet with eyewitnesses at a Pygmy village before setting his camera traps along the river. And it's in the dark of the forest that he'll witness something truly mysterious.

For generations, fishermen have told tales of sea monsters. One of the world's most legendary monsters is a sea serpent known as Cadborosaurus, or "Caddy," which has been reported off the coast of British Columbia for more than a century. But to science, it doesn't officially exist. Now Pat travels to Vancouver Island to track it down. He questions eyewitnesses, explores the myths of the coastal people who have occupied the area for more than 5,000 years and confers with top oceanographers. After drawing clues from lifelong deep-sea fishermen and performing cutting-edge examinations of marine anatomy, he treks to one of the most remote and least understood places on the planet for answers: the bottom of the ocean.

The Mongolian death worm is rumored to live in the Gobi Desert, one of the most inhospitable regions of the planet. This freakish creature is said to spray acid, send out electric shocks and explode when threatened. After traveling to the vast, empty wilderness, Spain dives in with the locals to garner some leads. To impress them, he finds himself in over his head- literally - fighting one of Mongolia's top wrestlers. Afterward, Spain earns the villagers' trust, and they divulge new information he uses to start his investigation. He treks to the Gandan Monastery, where death worm stories may have ties to shamanistic beliefs, and then consults written accounts from expeditions in the 1920s before heading out to the brutal desert on the hunt for evidence.

In the jungles of the Indonesian island of Sumatra, locals have reported seeing a creature that looks like an ape yet walks like a human. They've named it Orang Pendek, or the "little man" of the forest. Spain's assignment is to find out whether a new great ape is waiting to be discovered or if we have a strange new cousin. Journey with him on a pilgrimage to a respected shaman who provides further details of Orang Pendek and local folklore. Then, after another eyewitness provides consistent details, Spain ventures deep into the forest to find the proof himself. He'll team up with a local conservationist with a record of discovering new species in the area and endure a brutal trek through the elements. With cameras strategically placed, a photograph could give them the revelation they've been waiting for.

Deep in the Brazilian Amazon lurk tales of a massive one-eyed monster. With slashing claws, savage howl, noxious stench and a gaping mouth in its body, the locals tremble to repeat its name: mapinguari. To gather concrete information on the creature, Spain must gain the confidence of the local tribes. He takes part in an extreme initiation ritual: wearing gloves lined with venomous bullet ants. The insects' stings send Pat into a hallucinatory world of pain. Through this ordeal, he earns the trust of the forest tribe and is given the leads he is looking for. After meeting with a victim attacked by a mystery creature and a hunter who claims to have shot a mapinguari, Spain is introduced to an ornithologist who believes the creature is a relic population of prehistoric giant ground sloths. But it's a distinct animal call in the dark of the Amazon, mimicking the locals' descriptions, that energizes Pat's investigation.