If you just finally got over missing Joss Carter on Person of Interest, prepare for some emotional wounds to open up again.

On Person of Interest Season 4 Episode 20 tonight, we'll be treated to some flashback scenes that center on Taraji P. Henson... who left the series and hit the TV jackpot with Empire.

But this isn’t just a heartfelt remembrance episode; it's one in which Reese, caught in a perilous situation, has to deal with some of his personal issues, relying on Carter to help him through it.

To find out more about the change-of-pace installment we’re getting prior to the final two episodes of Person of Interest Season 4, I jumped on the phone with executive producer/creator Jonathan Nolan.

In the following exclusive Q&A, we find out why this was the right time to bring Carter back; what it means for Reese moving forward; and what we may see on the upcoming season finale...

TV Fanatic: Tell me how long this has been in the works. Did you know you were going to bring Carter back even as you were killing off the character?

Jonathan Nolan: Yeah, I think we had said in the follow up conversations to that episode when Carter was killed off. We always intended to bring Taraji back. We loved working with her and in cooking up a way to bring her character back, from that point onwards, it was last year I said we should come up with a killer way to bring revisit her character and showcase the emotional growth – or lack thereof – for Reese this season. His pretending to be a normal person and highlighting the fact that he is far from a normal person…Carter was always the character who could speak most directly to him and cut through the nonsense.

TVF: A lot of their scenes in the episode are static and sitting in the car but that’s what made me miss Carter and Taraji as well as their dynamic together. Did you and your writers feel the same way?

JN: Oh, yeah. We love Taraji, we love Carter’s character and the dynamic between them…each of the characters on our show, they’re unique. Finch and Reese have a way of engaging with each other has become very connected and very personal. It’s interesting. You have some people in your life you can talk to things about and Carter says this in the episode, ‘you can talk about everything but the real stuff.’ We love writing those scenes.

Actually, for all the things that happen on a given episode of Person Of Interest, those stakeout scenes are often so much fun to write because they really strip away all the nonsense and, on that level, it strips everything else away and people can talk.

TVF: Tell me about the cold case that Reese gets pulled into. You could have gone back to a lot of different cases but why this one?

JN: We wanted a case, really, to be a straight homicide. Obviously this one has its own twists and turns [and] the writers Erik Mountain and Melissa Scrivner Love pitched it and did a knockout job…we wanted a straight, cold-blooded perpetrator that Reese would stumble into. We all love storylines like this...Reese is pretending to be a municipal police officer so he has a day job so you get sucked into these very dark universes unto themselves and so we wanted a family story that the logic of which played out with the twists and turns and be complicated enough that Reese would put himself in real peril.

One of the things I’ve seen in other shows over the years is being a police officer is a very difficult job and part of the fear and anxiety of that job is you never know when you’ve stumbled into something that’s far more dangerous than you imagined. It can be fairly routine things that you’re looking into something and it blindsided you so we wanted that blindside and then we wanted the episode to collapse in a direction you don’t see coming.

It’s like Magnum PI in the fourth season opener, it was my favorite episode of that show called Home From The Sea. By this point, you’ve seen maybe 88 episodes of our show and you’re very familiar with the format and you’re very familiar with how it works so it’s fun to just get in there and f**k with them. [laughs] They think they know how the show works and then you can use that against them in a great way.

TVF: I have to ask, is the Magnum episode the one where he’s stranded out at sea on his surfboard [or scull boat] and he’s all by himself?

JN: Bingo! I love that show and it’s one of the things that I loved about that which is you’re very familiar with the format and [co-creator Donald] Bellisario comes back in and blows your head back. My contention is that ‘procedurals,’ which has kind of become a dirty word in television these days, but for fifty years, that’s what television was…I’ve always maintained that they were a delivery device for character drama.

You got to know these characters so well that these tiny movements, these tiny revelations and the things you learn about the characters in departure episodes like this are so hard won. You feel like you’ve known these people almost like you know a member of your family and then all of a sudden you discover something completely surprising. We had long looked for an opportunity to reveal a little more of Reese’s backstory.

TVF: What’s the impact on Reese moving forward after this episode? Do we see that it’s had an impact?

JN: Yeah, you do. [Episodes] 21 and 22 are jam packed and in terms of timing this is perfect. It was the right moment to work with Taraji and the right time to spend with the personal before, as we do each season, everything blows up in our faces in the last few episodes. But what I think we see with Reese, he’s gone through something and it has left his mark on him. In his relationships with Fusco and everyone else we see a little bit of a change. Obviously it’s still the character we know and love but he’s had a little bit of an emotional awakening.  

TVF: There are a lot of great lines in the episode like ‘They didn’t see it coming’ and ‘ever think about the future?’ I was wondering if that pertained just to Reese and this episode or are you nudging the audience to tell them to pay attention to what’s coming in the rest of the season. I’m being very suspicious here!

JN: Erik Mountain and Melissa Scrivner Love, who wrote the episode, layered it with dark secrets. We’ve always said the one thing you can take to the bank with this show is that it’s not going to end well for these characters. We’re playing with fire here with all these characters and it’s always good to remind the audience of that.

TVF: Thank you for a scene with Root in a wedding dress. It was awesome. Just wanted to tell you that.

JN: [laughs] The writers, Erik and Melissa, came up with that and we were delighted with it.

TVF: How would you describe the rest of the season? Is it going to be a showdown between the Machine and Samaritan? Or are there some new threats coming?

JN: Yes to all of those. We’ve always been able to put on a spectacular for our last couple episodes and this is no different.

Person of Interest Season 4 airs Tuesdays at 10/9c on CBS. 

Jim Halterman is the West Coast Editor of TV Fanatic and the owner of JimHalterman.com. Follow him on Twitter.