Characters played by John Douglas
Self
Characters played by Dave Bellmont
Robert Ressler
Characters played by Gus Mahoney
Background talent
John Syzc
Characters played by Jacob Jensen
Young John Douglas
Characters played by Cynthia Smith
Clarnell Stage
Characters played by Andrew Stecker
Philadelphia Police Officer
Characters played by Josie Axelson
Shari Faye Smith
Characters played by Molly Ryman
Roslyn Falco
Characters played by Emily Sue Bengtson
Dawn Smith
Characters played by Tyler Noble
Postal Worker
Characters played by David Tufford
Parole Board Member
Characters played by Lucy Lawton
Rosalind Thorpe
Characters played by Tyler Carlson
Young John Wayne Gacy
Characters played by Kyra Richardson
Sandra Lindsay
Characters played by Sean Dooley
Bob Smith
Characters played by Rebekah Hasenmueller
Rosemary Keenan
Characters played by Ava Egertson
Josefina Rivera
Characters played by Brian Cristofono
Lexington County Detective
Characters played by Sam Landman
John Wayne Gacey
Characters played by Konrad Case
Ed Kemper
Characters played by Audrey Parker
Valentina Suriani
Characters played by Casey Radmann
Detective
Characters played by Erin Roberts
Postal Worker
Characters played by Andy Voyen
Background Talent
Characters played by Shelli Manzoline
Becky Broder
Characters played by Nels Lennes
Larry Gene Bell
Characters played by Ben Shaw
Gary Heidnik
Characters played by Reese Britts
Attica Corrections Officer
Characters played by Charlie Nunn
Young Gary Heidnik
Characters played by Melinda Korich
Parole Board Member
Characters played by Max English
John Wayne Gacy as a child
Characters played by Nelson Morlock
FBI Camera Operator
Characters played by Hannah Nelson
Background Talent
Characters played by Albert Melloy
David Cram
Characters played by Savannah Cherry
Background Talent
Characters played by Aimee K. Bryant
Parole Board Member
Characters played by Andrew Wheeler
Gacy's Father
Characters played by Steven Wothe Jr.
Detective
Characters played by Trevor Keeth
Enforcer
Investigator
Characters played by Jon Steinhorst
Corrections Officer
Characters played by Alec Leonard
Carl Denaro
Characters played by Brandon Brooks
Timothy McCoy
Characters played by Cassie Osuji
Deborah Dudley
Characters played by Jessa Frankenfield
Alice Liu
Characters played by Matthew Branch
Officer Burton
Characters played by Julian Felder
Background Talent
Characters played by Michael Hundevad
Alexander Esau
Characters played by Nick Wright
FBI Sound Mixer
Characters played by Abby Assefa
Background Talent
Characters played by Avi Ahroni
David Berkowitz
Characters played by Emily Dooley
Hilda Smith
Characters played by Henry Smith
Young Ed Kemper
Characters played by Hamed Hagi
Background Talent