When teenager Rob Piest goes missing in the Chicago area, the prime suspect is revealed to be an affable and well-liked local businessman named John Wayne Gacy. As officers tail, interrogate and eventually arrest Gacy, it becomes clear to the Des Plaines Police Department that the young man is just one of many who have disappeared at his hands. Lieutenant Joe Kozenczak and Detective Rafael Tovar lead the investigation that uncovers the remains of 32 young men and boys Gacy murdered, as well as the holes in the system that allowed Gacy to evade detection and capture for more than seven years. Meanwhile, a rivalry ensues between Gacy's lead defense lawyer, Sam Amirante, and the local prosecutor, William Kunkle, as the former tries to prevent Gacy's execution while the families attempt to understand how and why their sons were taken from them.