Cave guide Keven Neff's Wild Cave tour through Mammoth Cave turns wildly adventurous after the tour poses for photographs in the Snake Pit for his friend and retired cave guide Bob Cetera. A Homeland Security agent sent to assess terrorist threats to cave tours becomes the least of Keven's problems. Shortly after leaving Bob's photography group, Keven encounters a ghostly lantern floating across the cave passage. Keven calls on Bob and Walt to investigate while he tries to keep his tour on time. Near Cathedral Domes, Craig, a visitor, lags behind to make a call on his smart phone.

After a deafening buzzing, Keven and the tour find themselves in what looks like the same cave passage, but fresher somehow. Craig is missing, and the trail is littered with rocks that they didn't hear fall.

When the tour fails to show up on time, the park rangers search, but find only Craig sitting in the dark, apparently suffering from a nervous break down.

Rejecting the ranger's idea that Keven is lost, Bob mounts his own search with his friend Walt and the rescued Craig. They reconstruct the chain of events that led to Craig being left alone in the dark and decide to follow Keven: not knowing where he went or if he survived.