Investigators Conrado and Fernando take a leave of the absence from the police force to track down Fernando's girlfriend Virginia. Virginia, a reporter, has left town and is working undercover as a barmaid in order to interview Refugio Canales, a criminal and small town municipal president. Conrado and Fernando soon call their friend Santo for help.

The evil scientist Dr. Caronte plots to revive the brains of three dead scientists and use them to obtain the formula for the super-powerful neutron bomb. The resulting creation needs blood lots of blood, sending Caronte's midget assistant Nick and his legion of mutant monsters out to get fresh victims. However, the masked atom-superman Neutron vows to put a stop to Caronte's deeds.