1865: Three intrepid ladies team up with uncanny ancient mountain spirits. Their loved ones are lost inside a mountain in a gigantic cave system in the Alps. To free them they seek supernatural help which is as strange as it is frightening.

In the caves, a ruthless inventor is secretly developing a terrible weapon. The mythical Fey are to be processed as ammunition.

Charlotte rescued one of the Fey from captivity and is led through the dark tunnels by an eerie companion who is by no means as harmless and nice as she thought. A fiend from the darkest abyss of time hunts its prey in the caves, and more and more trapped men and women prepare for an unequal fight the outcome of which threatens to mean death for all of them.