An upstanding doctor is transformed into a cold-blooded serial killer after being attacked by terrorists in Vietnam.

On the day of his first communion, the boy Honorato is orphaned because the mafia murders his parents. Before dying, the father recommends that the son defend himself against whoever tries to harm him, so that over time he becomes a bloodthirsty and sadistic gunman, always accompanied by the ghost of his father. His fame bears in the ears of Rutilo, the boss of the central supply, who hires him to avenge the death of his son. Honorato fulfills the mission with luxury of violence and becomes a trusted man of the gangster.

Tells the parallel stories of nine-year-old Carlitos and his mother, Rosario. In the hopes of providing a better life for her son, Rosario works illegally in the U.S. while her mother cares for Carlitos back in Mexico.

A widowed veterinarian and his son who claims to speak to animals are captured by the Chinese mafia in 1920s Mexicali and forced into the city’s hidden tunnels, where a mythical creature awaits to change their fate.