John Wayne Gacy becomes a prime suspect in teen Robert Piest's disappearance. Previously unheard audio tapes reveal Gacy's thoughts and early days.

After a sprawling confession, Gacy starts acting erratically, forcing police to contend with both his behavior and a shifting investigation.

As Gacy's lawyers try to mount an insanity defense, police attempt the daunting, emotional task of identifying — and honoring — each of his victims.