Ruins of Hidden Evil

Tunnels filled with human bones beneath the streets of Paris and ruins of a massive industrial operation contain a haunting past; experts investigate the evil secrets behind these deserted places to uncover how they were built and why they were abandoned. This is a mashup of S06E02 "Swamp of Despair," S04E04 "Labyrinth of the Dead," and S07E02 "American Ghost Park."