The Underlying Evil is a suspense-drama set in the sport of bodybuilding. The main theme is the effect of anabolic steroids on the lives of the characters.
The plot centers on a father's emotional separation from his son because of anabolic steroids. The son, Tim, is a competitive bodybuilder using steroids to win a major contest and turn professional. The father, Paul, is angry that Tim is using drugs and wants him to stop. Neither individual will relent, dividing them in anger. Tim must deal with his father's anger while training for the biggest contest of his life and juggling an elusive girl he is desperately in love with. Various events, including a lucrative contract to endorse products for a fitness firm, drive him deeper into bodybuilding as he pursues his goal. However, the death of a friend and the revelation that his steroid use is affecting the people around him, lead him to make an important decision about bodybuilding. Paul is a former competitive bodybuilder who blames himself for exposing his son to the sport. We experience his journey from a beginning bodybuilder to a champion and his ultimate rejection of the sport because of steroids. Finally, just as his relationship with Tim begins to mend, a character from his past comes back to shatter his present.
A subplot focuses on a ruthless bodybuilder willing to do anything to win and turn professional. Through him we are exposed to another side of bodybuilding and the reckless behavior heavy steroid use will generate. He commits a murder, linking him to a savage criminal he must turn to for help and who plagues him throughout the story. The criminal is a member of a crime ring that buys steroids from the black market and distributes them nationally through a chain of commercial gyms. The ring is run by an indiscriminate profiteer shamelessly spreading steroids throughout bodybuilding and aiming to govern the sport. Within the ring is a reluctant doctor administering steroids to bodybuilders and handling the logistics of distribution. He is targeted for arrest by an undercover vice detective seeking to shut the ring down.
Depicted are the world of competitive bodybuilding and the steroid use beneath the surface. Together the characters race toward an unknown ending in which none of them escapes unscathed.