Lupo and Bernard investigate the murders of the Morgan family: parents, teenage daughter Zoe, and young son all stabbed in the neck with a knife. The detectives are keen to find Zoe's friend Bonnie, who was over at the Morgans' house on the night of their deaths. Bonnie is staying at a halfway house where another resident, Freddy, has now been murdered. He was killed with a knife through his neck, the same as the Morgans.
From a search of Freddy's computer, the detectives locate Bonnie along with Zoe's boyfriend Justin Sachs. He is a Juggalo and a fan of violent horrorcore rap. Bonnie claims not to remember her name or her parents. When her picture is posted online, she is identified as Amanda Evans,a runaway that Justin protected when she came to New York City. Because of her fragile mental state, McCoy agrees to have her remanded to a psychiatric facility.
Justin's defence is that he suffered from PTSD and became obsessed with violence after seeing graphic news footage of the 9/11 attacks when he was a child. Amanda tells the jury that Justin became enraged and killed the whole Morgan family because he found out Zoe was cheating on him. But his lawyer, Veronica Masters, asserts that Amanda clearly isn't credible since she wasn't fit to stand trial herself.
Lupo begs Cutter not to allow Masters to cross-examine him but Cutter cannot do anything about that.
Lupo confesses to Bernard that he met Masters during a previous case of a man who killed his entire family. The crime scene was so horrific that Lupo developed PTSD and a drinking problem. When he's called as a witness at Justin's trial, Masters asks Lupo about the previous case. He tells the jury the whole story, including his former partner being killed while Lupo was drunk on duty.
Cutter, who has researched Masters and Lupo's previous case, reveals to the jury that Masters used PTSD as a defence on that occasion too - but it didn't work. Masters accepts defeat and takes a plea for Justin. Later, Lupo and Bernard attend a crime scene together and are warned that it's very disturbing. Lupo reassures a concerned Bernard he'll be fine.
- A Deadly Affair: Justin killed Zoe because she had started seeing another guy on the side.
- Asshole Victim: Freddy was a pimp trying to take advantage of a teen runaway.
- Big Brother Mentor: Justin was this to Amanda.
- Empathy Doll Shot: The murdered body of the Morgans' young son is surrounded by some of his toys.
- Mass "Oh, Crap!": Jalisa and Eric Kroger have this reaction upon seeing their daughter Sasha held hostage at knifepoint by Amanda.
- Patched Together from the Headlines: Based on several contemporary issues.
- Moral panic over Juggalos, media violence, and websites hosting extreme gore.
- The 2009 Farmville, Virginia murders
- A news story about an amnesiac teenage runaway being found in Manhattan
- Then-recent studies about PTSD caused by footage of 9/11.
- Suicide by Cop: Amanda attempts this with Lupo. Luckily for the latter, it doesn't work.
- Would Hurt a Child: Justin murdered the Morgans' young son and Amanda holds an eight-year-old girl at knifepoint.
