At the scene of the murder on a rainy night, the forensic doctor dug out a strange bronze key from the corpse's clenched hand.
The key has a strange pattern and seems to point to a local old hospital that has been abandoned for thirty years.
As the investigation deepens, she discovers that this is not an isolated case. Similar keys and bodies appear every ten years.
And all the clues vaguely point to her father, who is also a forensic doctor but has been missing for many years...
