Human bones line a sprawling maze of tunnels beneath the streets of Paris, and this gruesome labyrinth is evidence of a devastating horror; new discoveries reveal the secrets of this strange place and why it was abandoned. This episode is a mashup of S06E04 "Hell on Blood Island" and S04E04 "Labyrinth Of The Dead."

The site of strange, alien-like structures hidden deep within a remote forest was once one of the deadliest places in the world, and new evidence reveals who built these bizarre ruins and why. This is a mashup of S06E05 "Florida Doomsday Castle" and S04E09 "Haunting on Plague Island."