In Tijuana, Mexico, Gabriel is a man who once had a normal and happy life alongside his family. He now seeks revenge for the murder of his son at the hands of a group of vampires that roam the city at night, stalking its inhabitants. Gabriel's days blur into one another as he tries to track down the murderers he calls "leeches", without knowing that his revenge will bring serious consequences for his wife and himself.

A married couple loses their children while on a family trip near some caves in Tijuana. The kids eventually reappear without explanation, but it becomes clear that they are not who they used to be, that something terrifying has changed them.