Former FBI Agent Candice DeLong takes a look back at one of the most memorable cases she studied. From the haunting message the killer scrawled in lipstick on the wall of the female victim's apartment in Chicago in 1945, the press nicknamed him "The Lipstick Killer." Candice unravels how the murderer, William Heirens, escalated his criminal career from seemingly petty "nuisance crimes" to sexually-motived homicides.