Dark are the Steps of Time by Lance S. Barron

Title: Dark are the Steps of Time
Series: The Longest Dark: Mammoth Cave Guides (Book Two)
Author: Lance S. Barron
Genres: Mystery and Sci-fi
Audience: Mature
Released: 11/10/2015
Price (USD): $2.99 eBook, $16.95 Paperback.

Vibes: Time Travel, descriptions of parts of Mammoth Cave, coping with the unexpected time travel including how to talk about Mammoth Cave with an enslaved guide in 1838.

Synopsis:

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.