The Mercy Falls Children’s Hospital is about to close its doors for good after one Century of service. But the closing process is taking longer than expected; a railroad accident has left the local hospitals without beds.  It will take a few more days to transfer all the children. It will not be an easy task. Most of the personnel have left and practically all the installations have already been dismantled. Amy, a young nurse, is sent from London to help out but she soon detects something odd in this place.

The children are nervous and afraid of something intangible, invisible. Something that shouldn’t even exist. Something full of pain. And hatred. Some of them call it "the mechanical girl".

And they claim it lives upstairs, on the third floor. The floor that has been closed and blocked away from the rest of the building for 40 years. And little by little, this presence begins to make itself increasingly evident. More aggressive. Moving through the hospital’s corridors. Crouching in the shadows. Because this hospital holds a secret. Something terrifying that has returned from the past. Something that shouldn’t be here.

And to discover it and protect the kids, Amy must face everything: the rest of the hospital staff who refuse to accept the obvious, her own fears, and the truth. But the truth is very far from what anyone suspects. Darker. More sinister. And more dangerous.