Warning: SPOILERS ahead for Dexter: New Blood episode 9.

While Dexter is informing Harrison about the Code in Dexter: New Blood, Deb stops him right before he tells his son about his blood slide kill ritual - which will help Harrison in the long run. As the original Dexter series reminded viewers, serial killers almost always keep a trophy as part of their kill rituals to remember their victims. Dexter’s Bay Harbor Butcher ritual was cutting his victim’s cheek and placing the blood sample in a slide that he would keep in a box, which was one of the most sociopathic aspects of his vigilante serial killing - and almost got him caught several times.

After Kurt tried to kill Harrison as the Runaway Killer in Dexter: New Blood episode 8, Dexter decided it was time to tell Harrison about his own Dark Passenger and, more importantly, the Code of Harry. New Blood episode 9 kicks off with Dexter telling Harrison about the Code through a flashback of him hunting and capturing Wiggles the Clown, an unseen kill from the original series. As Dexter tells Harrison of his process step-by-step, he gets to the part in the flashback where he has Wiggles on his table and is about to cut his cheek for his blood slide trophy before Deb interrupts and tells Dexter he can’t tell Harrison about his “sick-a** ritual,” so Dexter skips over this detail.

Related: New Blood Retcons Dexter’s Bay Harbor Butcher Drug

Considering Dexter’s initial story to Harrison in New Blood included every aspect of Dexter's Bay Harbor Butcher M.O. aside from his blood slide ritual and actual killing of the victim, it was extremely significant that this detail was excluded. The most important reason why Deb would stop Dexter from telling Harrison this is because it’s much sicker than just being a vigilante - it proves that Dexter has a sociopathic need to remember and re-experience these kills with gratification. Dexter tries to frame the Code as being non-lethal or particularly disturbing, as he strategically ends the flashback by saying he just scared Wiggles into never hurting anyone again. If Dexter had included the fact that he kept trophies and sadistically cut the cheeks of his victims, it would prove that the Code wasn’t just about controlling his urges, but that he enjoyed the violent process.

In Dexter: New Blood, Dexter is trying to fix where Harry went wrong in teaching him the Code, especially since he believes that Harry turning him into a monstrous killer was “child abuse.” By excluding the ritualistic trophy that came from Dexter’s Bay Harbor Butcher career, he’s trying to avoid passing on the same sociopathic gratification of reliving his crimes, even though they’re against “bad people.” Dexter realizes that the blood slides were never part of Harry’s Code because they went against the idea that he was just a vigilante, making him just as much of a sadistic serial killer as the rest. Instead of passing on this disturbing ritual to Harrison that would just feed the gruesome aspect of his Dark Passenger, Dexter leaves it out so that Harrison doesn’t believe this is okay. Even when the two team up to kill Kurt, Dexter doesn't cut his cheek or take a blood sample.

Considering Harrison is apt to take each aspect of the Code seriously in Dexter: New Blood to satisfy his own Trinity Killer-made Dark Passenger, it was extremely important that Dexter leave out the blood slides so as to avoid being caught. Rule number one in the Code is to not get caught, and Dexter’s blood slides almost led to him being found out as the Bay Harbor Butcher on multiple occasions in Dexter’s original series. Trophies and specific rituals in M.O.s are some of the most common ways that serial killers get caught, which is what made Dexter’s blood slides one of the most dangerous aspects of his ritual. Dexter has let Harrison in on the “family business” in Dexter: New Blood, but he also needs to exclude the riskiest aspects of his rituals.

Next: Dexter: New Blood Is Finally Fixing A Deb Problem After Her Death

Dexter: New Blood releases new episodes Sundays on Showtime.