The ruins of a great wall that once marked the edge of the world hold the secrets of the ancient soldiers who stood watch here long ago; new discoveries reveal who the wall was meant to keep out and why the site is littered with skulls. This episode is a mashup of S06E03 "End Times on Lake Michigan" and S05E02 "American Atlantis."

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."