The dank catacombs beneath the teeming streets of Paris conceal some nasty surprises in John Erick Dowdle's subterranean horror.

Scarlett (Perdita Weeks) is a gung-ho tomb raider and academic, who hopes to complete her late father's quest to uncover the resting place of the fabled Philosopher's Stone.

This odyssey leads her to the spooky catacombs of the French capital, which houses the remains of six million dead, in the company of friend George (Ben Feldman) and cameraman Benji (Edwin Hodge).

Locals Papillon (Francois Civil), Souxie (Marion Lambert) and Zed (Ali Marhyar) join Scarlett and her team on the quest to unravel the secrets of the Parisian underworld but as the treasure hunters venture into the darkness, they come face to face with shocking visions from the past, which systematically drive each member of the expedition to the brink of self-destruction.