Endeavour Morse’s affection for ale and whiskey is one of the character quirks Colin Dexter wrote into his detective in his novels. When John Thaw brought “Inspector Morse” to TV in the 1990s, audiences came to accept Morse and Sergeant Lewis’ (Kevin Whately) regular pops into the pub to mull over a case while enjoying a pint.

Morse’s habit was part of his persona in the original series. Its prequel “Endeavour,” set in the ’60s and early ’70s, establishes that the detective didn’t start out that way. But the years have taken a toll on Shaun Evans’ Endeavour Morse, and as the three films that comprise Season 8 show us, his drinking habit is getting in the way of his relationships and his ability to do his job.

In Sunday’s season finale “Terminus,” Morse doesn’t so much solve the case as salvage it, not before he’s warned by his mentor and partner DCI Thursday (Roger Allam). “The drink’s a good servant, but a poor master,” Thursday tells him, adding later, “You’re young. You’re smart. Break the habit before it breaks you.”

In an interview prior to the finale’s Stateside debut on PBS, series creator Russell Lewis tells Salon that it was Evans’ idea to investigate his character’s relationship with drinking, an especially poignant choice given how close the series is to ending. Lewis is fond of writing subtle Easter eggs into “Endeavour”; one that acknowledges the drama’s curtain call is nearly upon us comes at the episode’s end when Morse casually takes in the snow-crusted landscape and remarks, “Beginning to thaw.”

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This also means the creative developments Lewis and Evans explore in this version of Endeavour Morse may impact the way people view the inspector that Thaw made famous, as Lewis explained to Salon in a recent interview conducted over Zoom.

The cast and crew are currently in the midst of filming the ninth and final season in the U.K., which Lewis teased a bit during our conversation. Beforehand, we talked about the purposeful handling of Morse’s alcohol dependency and why Evans was keen on leaning into that side of his character.

This interview has been edited for length and clarity.

People have noted the puzzle hints throughout the season, and particularly in this finale, indicating that the bridge between “Endeavour” and “Inspector Morse” is solidly visible now.

I mean, that’s always been underpinning everything we do, really, from the start. Obviously, there’s going to be a sort of 15-year gap between our ending and its beginning. We always based it on the televisual incarnation of Endeavour Morse rather than Colin’s books, which  if we were following that, he’d be an inspector within three years, by 1975. So we’ve always cleaved to the TV incarnation as being the thing we have to link up to, basically.

All I ever wanted, really, was to fill in some of those blanks and solve some of those mysteries about his character. With any retrofitting show, you’re having to map your own geography. There’s hints and clues in the series, there’s hints and clues in the books. And we just drew on those to feather in his background, I guess.

He’s still I think, in story time, he’s around about 30, early 30s. I suppose I always felt by the time we got to “Morse” when I was watching — when I was younger — you know, he’s a middle-aged guy. So [Endeavour] is not going to be that middle-aged man by the time we get to the end, I suppose, is a long way of saying that.

Just as a refresher, I looked at the finale of “Inspector Morse” to see how he ended. As series finales go, it’s a pretty famous closer. In particular, there’s a scene where the doctor said, in so many words, “If you take care of yourself and stop drinking so much, maybe your heart won’t give out.” And he essentially refuses to do that. Did you watch that before you started on this arc?

No. I mean, I kind of I watched them all when they were on originally. And those sort of things kind of seep in, I guess. I hadn’t forgotten them in the interim. But no, I didn’t. It wouldn’t have been helpful, going back and rewatching it all. With those waypoints in mind, we set out on winding up our part of the journey. Should I wish to do it, there’s 15 years I’m told still. But we’re happy to bow out when we’re bowing out, I think.

What were the parts of the puzzle of Endeavour Morse that you wanted to make sure to click into place as you progressed, not only for these final episodes but since the start?

When we started, we didn’t want the audience to feel that all of those pieces were in place. So our job over these 36 films, I suppose, has been to knock the emotional, soft stuff out of him, if you’ll forgive me. To constantly apply pressure to him psychologically and emotionally to get him to a point where you could see, oh, yes, that’s how he became who he is. You know, the child is father to the man. But we wanted to start out with a fairly optimistic, hopeful young man, and take him apart bit by bit.

He was never playing from a position of strength with his early life: losing his mother, a rather unsympathetic stepmom, not a great relationship with his father. A stranger in his own house, really, from about the age of 12, after his mother dies and goes to live with his father and stepmother. “Oh what a lonely boy.”  I suppose that that was the jumping off point.

Endeavour (Courtesy of Mammoth Screen and MASTERPIECE)

Also, he’s made of different stuff. The things that speak to him are not the things that spoke to the people that he was living with as a child, or a young man.

By the time we meet him as the young detective, he’s all corners, you know. He’s kind of spiky and edgy,  but filled with this desperate longing to connect with another human being. And that’s where we came in with him, really, to see how that might eventually be molded through circumstance into an approximation of the later incarnation of Morse. And it’s been a great pleasure over the last 11 years to knock holes out of him, psychologically, emotionally.

The drinking in this season was something Shaun very much wanted to do. What I didn’t want to do, I didn’t want to do a heroic drunk. Because that I find a bit dishonest.

Well, let’s expand on that, because certainly there are a number famous cop shows that, as you say, feature heroic drunks. “NYPD Blue” is one classic that comes to mind, specifically Detective Andy Sipowicz.  In this season’s finale mystery, his drinking problem becomes an impediment to solving the case. How did you formulate that twist?

I mean, it’s a spur that makes him turn it around, I think. You have to touch bottom before you can kind of start to come back up again. And I think for him, he’s a fairly dignified character, you know. He a man who loves literature and music. And falling down stairs on buses, is probably not what he aspires to. But particularly when it had such ramification . . . you know, the one thing he’s always been able to hold on to, and it’s the thing that’s kind of cost him dearly in his relationships, has been his brilliance as a detective.

When Thursday realizes  what took place on that bus, I think that’s the big thing that pulls him up short. The heroic thing after that is he tries to straighten out. I think that’s the heroic thing.

Audiences accept certain quirks and habits in their TV detectives, don’t they? With “Inspector Morse,” his habit of drinking a pint of real ale and whiskey was just a part of his character. But this changes the way we look at that, doesn’t it?

Completely. Well, it was as much about addressing a request from Shaun that we go down that road. But you’ve also got to find a way of leaving him intact by the time we finish what we’re doing, which is a functioning alcoholic.

We’ve had Max talk about it in the past, I think, Dr. Debryn? “Such-and-such character liked a drink,” you know. That’s the euphemism for a kind of alcoholism, or borderline alcoholism or functioning alcoholism.  So that’s where we’ve got to leave him.

I think that the views of “Morse,” you know, probably didn’t quite see it to that degree, that he’s a functioning alcoholic. But that is, in fact, what he is. It’s managing it and so he doesn’t go down with the kind of blackouts that he’s having, which we depict in the last film. But he manages it, you know. It’s something he does and just keeps himself at a certain level in later life. But it’s the slow poison, isn’t it, that eventually does for him.

Let’s back up, because you said that Shaun really wanted to do this. Why?

I think as an actor there are places that you find really interesting to explore. He’s looked at the books, that’s one thing he has done, which is look to the books now. He’s coming at it from Colin’s novels as much as anything else.

But he always looks for a journey with each series. That was the journey that he was keen on for this one. I kind of found the halfway place that we could meet really.

Do you think this kind of changes our relationship with the original guise of the character that John Thaw gave us so long ago? Because in “Inspector Morse,” he’s presented as a curmudgeon, but he’s also very good. And those qualities inform the interplay between, him and Lewis. Admittedly, it’s been a long time since I’ve watched all the episodes, but I don’t recall Morse’s drinking being interrogated as closely.

I think that’s it, isn’t it? I mean, I think times have changed hugely. And it’s a hard sell, isn’t it? I’m trying to remember exactly when “Cracker” started because “Cracker” embraced that with its sleeves rolled up with Robbie Coltrane’s Fitz, who was, you know, a gambling, drinking, smoking, absolute wreck.

But he still got the job done!

Right. That’s the heroic drunk. It’s a choice, you know. But I didn’t want to endorse that.

I don’t think it kind of undercuts anything that that that John did, or Kevin [Whately] did in the original series of 33 films. I think towards the end, you know, where you’ve got Morse in hospital . . . it’s all leading to the one place which isn’t the happy one. He’s checking out early 50s in the books, which isn’t a good look.

But we look past that because people do concentrate on the cozier aspects of the character. That’s probably why we’ve looked at it a little more dispassionately.

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One aspect of “Endeavour” that fans love are the subtle insertions of little puzzle pieces and hints throughout the dialogue. Given the way this season went, just in terms of the character focus, did that change your relationship with putting those puzzle pieces in?

I’m very aware that there are some people that tune in for the puzzle, and some people that tune in for the more domestic material. So it’s just getting that balance, right? I think. The puzzles are there for that side of the audience, but you don’t need to grasp it to enjoy it. But the information that we get is that people watch them more than once. Hopefully there’s other things for them to get on a second or third or fourth view.

You’ve got to have fun. If you’re not having fun, the audience is going to feel it.

What inspired the style and tone of this season’s third film, the finale? It seemed very Agatha Christie to me, and admittedly I’m being very general since I lack an intricate education when it comes to British mystery series.

Oh no, no. There are a few things went into it: There’s a TV show over here called “On the Buses,” which was a situation comedy. A bit like “The Honeymooners”, I guess, you know, but on a much more English scale. It’s a blue-collar sitcom, and it was hugely popular in the UK. So it was a kind of cross between . . . I wondered if you could have “Murder on the Orient Express” meets “On the Buses”?

It changed a lot, that story. Originally, it was much more down-the-line slasher piece. But in the rewriting, people felt a need for much more of an Agatha Christie-esque puzzle. So that was kind of added into it in subsequent drafts. But originally it was a straight-up slasher, I was interested in the idea of the Final Girl, that was where that one jumped off. What we do with all of these things is see if you can do it through an “Endeavour” filter. So you’ve got the basic idea of the story.

And I’d felt we hadn’t done a “spooky” for a while, so there was an idea that that that might be a slightly spooky addition.

I love that you call it a “spooky.”

Yeah. Because when we were doing four per season, it was easy to do a wildcard. One wildcard out of four. But when you’re only doing three, it becomes very difficult. That one was the wildcard.

Is production on the final season underway?

Yeah, we’re shooting the second film right now.

Are you able to hit the tones that you want to cover in these last films?

Oh, I think so. I mean, it’s a strange thing, isn’t it, after 11 years? It’s a bit like planning your own funeral, really. So that’s where we are with it. The first film is something people wanted to do for a long time, which kind of plays into his passion for music. And then the middle one is a, “Well, if not now, when?”-type story. Then the last one is – I’m working on right now, which gives very little away I’m afraid. But it’s the usual “Endeavour” collection, I guess. Hopefully it pulls it all together.

All episodes of “Endeavour” are available to stream on the PBS app and Prime Video.

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