At the site of America's deadliest avalanche, witnesses report bizarre apparitions and sickly feelings of dread. Phil and Jess venture deep into Washington's Cascade Mountains to investigate a shocking cover-up and test a mind-bending scientific theory.

Deep in the Peruvian jungle, where deadly wildlife lurks at every turn, a supersized beast is terrifying locals. Phil tracks what could be an unknown species, while Jess hunts for evidence that a legendary creature known as Yacumama is on the hunt.

Phil and Jess probe the science behind geology's strangest phenomena while investigating mysterious objects flying around Mexico's tallest active volcano.

Jess and Phil venture deep into the Ozarks to investigate a mysterious predatory beast. Eyewitnesses, surveillance footage and new recordings of bone-chilling howls lead the team to a shocking revelation about the legendary creature.

Phil and Jess search whitewater rapids and a frigid Alaskan lake for a legendary beast that's now the target of serious scientific inquiry. Armed with new eyewitness accounts and advanced underwater robotics, the team takes a deep dive for answers.

In the Yucatan, Phil and Jess investigate watery caverns believed to be portals to the Maya underworld. Some say angry spirits are to blame for strange lights and bizarre animal behavior, but the sacred cenotes hide secrets far darker than any legend.

Braving shark-filled waters and deadly undersea tunnels, Jess and Phil probe reports of the Lusca, a sea monster said to be attacking Bahamian locals. Their hunt takes them deep into unexplored “blue holes” -- and could expose shocking military secrets.