With just one episode of “The Night Of” left in HBO’s arsenal, a clearer picture of the truth is beginning to unfold around the Nasir Khan case. As if there weren’t enough theories floating around, Sunday’s (Aug. 21) episode of the series adds a new suspect to the mix: Detective Sergeant Dennis Box (Bill Camp).

The man has been right under our noses the entire time, and while the concept of him being an accessory to the murder of Andrea Cornish (Sofia Black-D’Elia) sounds outlandish, let’s take a brief trip through the facts as displayed in Episode 7, titled “Ordinary Death.”

  1. Det. Box is heading into retirement.
  2. He quickly honed in on Nasir as the killer.
  3. He disrupted a crime scene for the comfort of the suspect.

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Let’s go through these one by one …

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For a seasoned professional such as Box, the end goal of retiring from such a leadership position probably comes with a huge weight lifted off of his shoulders. With all the violence and death he has viewed throughout his career, a permanent vacation is probably just what the doctor ordered. No way does it feel like he’d want anything to stand in his way.

With the finish line in sight, Box’s suspicion of guilt against Nasir Khan (Riz Ahmed) has been quite strong since the knife reveal in Episode 1. Yet, the way he communicated with Naz — while completely convinced he killed the girl — was as if he was walking on egg shells, while wearing kid gloves.

It was almost as if he knew the kid was innocent, even though he was guiding him towards his death sentence. Box still did what he could to make him feel any semblance of safety or comfort.

Now, here’s where we get to the interesting turn in the story as it played out in the final minutes of the episode. When Box is summonsed to return to the stand, Chandra (Amara Karan) questions him regarding Nasir’s asthma inhaler.

the night of asthma inhaler1 The Night Of killer theory: What is Detective Box hiding?

Why would Box remove evidence from a crime scene? After working so long in a field such as this, the dark realities of the job have probably done their part in hardening the man. Yet, as soon as he meets Naz, his empathy takes over? While that could very well be the reasoning for his decision, we have some deeper thoughts as to his true motive.

In Episode 1, John Stone tells Naz about Box, saying:

“Box is the senior man here. He got that way by doing what he does well. He rolls up his sleeves, delegates nothing, takes all things personally. I’m not saying he’s a bad cop. On the contrary, he’s very good. And like all good cops, he does you over just inside the rules. He’s a talented oppressor. Subtle beast.”

A subtle beast? Interesting …

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What if — and this might be a big what if — Box got involved with the wrong people on the other side of the law? We’re not sure exactly how, but when you’re deep in the worst cases New York has to offer, sometimes doing the right thing involves doing a wrong thing. At least, that’s the frame of mind as presented in shows like “The Wire” or “The Shield”. But hey, we’re not saying Box is on the same level as Vic Mackey (Michael Chiklis) … yet, given his second appearance on the stand, we are saying he’s not completely innocent either.

Our previous theory has Freddy (Michael K. Williams) connected to Angela’s murder — and we still believe he’s connected to the real killer in a familial or business relationship. We also know Freddy has his ear on the streets, even while in lockup, and let’s not forget about those under-the-radar agreements he has going with those prison guards as well. So, with that all in mind, how far fetched would it be to suggest that Freddy and Det. Box have ties?

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If that turns out to be the case, then it’s possible Box knew about the murder of Andrea Cornish before entering her brownstone to inspect the crime scene. Further, if he tipped off Freddy about Naz’s arrest — and that he’d be incarcerated for the killing — Freddy’s mentoring of Naz would make complete sense.

Why would Box take such actions? It’s possible he owes Freddy a favor from something in his past. And whatever that is, it may have been looming over his head as he stared down the barrel of this retirement.

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If this theory has any sort of merit, that’d find Box with a debt paid towards Freddy, while his shady dealings on the streets continue without interruption.

We could be completely off-base with this idea. Yet, it would make sense after seeing Box’s reaction as he viewed a murder victim earlier in the episode — who fits the same murder profile as Andrea. And given Detective Box’s somber state as he attempted to celebrate his retirement, it’s hard to not see the dark cloud above his head growing bigger by the moment.

“The Night Of” finale airs Sunday, Aug. 28, at 9 p.m. ET/PT on HBO.