Drowning City

After an accident in the Mexico City subway system, the detective Ulises Elizalde is sent to investigate. Ulises follows after a man who punches him on the subway tracks and he accidentally falls into the sewers. Underground he is rescued by Yamel a young woman who's hiding an enormous secret. It's later revealed that Yamel, and the other people living in the sewer drain have been injected with an eternal youth serum that was developed by a sciencist named Igor, under the orders of Milosz, an evil scientist from the late sixties. That's the reason why Yamel, who in actuality is 65 years old, has the appearance of a 25-year-old women.