SPOILER ALERT: Do not read ahead if you have not watched “Bagman,” the eighth episode of “Better Call Saul” Season 5.

Jimmy McGill’s descent into Saul Goodman has been on full display in Season 5 of AMC’s “Better Call Saul,” and on Monday’s episode, it took an even more dangerous turn.

Much to the concern of his now-wife Kim Wexler (Rhea Seehorn), Jimmy (Bob Odenkirk) is becoming a “friend of the cartel,” as he represents the show’s current main villain — Lalo Salamanca (Tony Dalton), currently behind bars on murder charges.

In Episode 8, “Bagman,” after Jimmy/Saul manages to trick the judge into setting bail (thanks to information from Mike Ehrmantraut), Lalo dispatches him to the desert. It’s supposed to be easy, Jimmy/Saul tells a worried Kim, and he even convinces Lalo to give him an extra $100,000 for his troubles.

In the worlds of “Better Call Saul” and “Breaking Bad,” there are always complications, of course. After grabbing the money from twins Leonel and Marco Salamanca (“the cousins,” played by Daniel and Luis Moncada), Jimmy/Saul is ambushed and nearly killed — until Mike (Jonathan Banks), who had been tracking Jimmy/Saul from a distance, appears and assassinates most of the would-be thieves.

One of the thieves gets away, however — and with their vehicles destroyed by the shootout, Jimmy/Saul and Mike are forced to stealthily march across the desert with the money in two large duffel bags.

It’s the moment that brings Jimmy/Saul and Mike permanently together — an uneasy partnership later seen in “Breaking Bad.” It also provides more foreshadowing for what ultimately happens between Jimmy and Kim, as Mike is incredulous that Jimmy told his now-wife about the money exchange. “She knows, she’s in the game now,” he says.

With little water and the blazing New Mexico sun, both Mike and Jimmy/Saul are soon sunburnt and parched — and Jimmy/Saul must even drink his own urine to survive. For “Breaking Bad” creator and “Better Call Saul” co-creator Vince Gilligan, who returned to direct the episode, “Bagman” was perhaps the most challenging episode to helm of his entire career.

According to Gilligan, it took 18 days to shoot “Bagman” (compared to the nine-day shoot of a typical episode), partly because so much of it had to be shot in the desert, two hours away from where “Saul” normally shoots in Albuquerque. The shootout scene, alone, took multiple days to pull off.

“It was something I was very much looking forward to, although I was nervous about pulling it off,” Gilligan tells Variety. “So much happens. I think it was probably the most complicated single scene I’ve ever directed, and that’s counting the movie [‘El Camino’] and everything I’ve ever done. Going back to the ‘X-Files.’ It’s enormous.”

With Jimmy/Saul now all in — and indebted to Mike for saving his life — “Better Call Saul” is now heading fast toward the events of “Breaking Bad.” Gilligan is back in the writers’ room (having previously stepped away from the show), which is currently breaking the show’s sixth and final season.

Here, Variety catches up with Gilligan to discuss “Bagman,” and what’s coming next.

This is sort of your “Lawrence of Arabia” moment.

That’s good. I like that. We did use a long lens. We were trying to figure out how to make it as “Lawrence”-like as possible. To the point where [co-creator] Peter Gould wanted to look into renting the actual “Lawrence” lens, which is apparently still out there, and maybe even still available for rent. That would have been good vibes, but I was I was too afraid we’d break it!

What were some of the challenges in shooting this episode?

A typical schedule is a nine-day schedule, but we knew right from the get-go that this would be more than nine days. I think our original thought was maybe it would be 11 days. Ultimately it was one episode for the price of two. I think we wound up going somewhere around 17 or 18 days. I was a Megillah, it was something else.

How did you end up directing this one?

There was a slot I could fit into [to direct an episode] once I finished up the post production for “El Camino.” And so I said to [executive producer] Melissa Bernstein and Peter Gould, “If you guys want me, it would turn out to be Episode No. 8.” And Peter started rubbing his hands together. He said, “Oh man, we’re going to give you a good one!” And I would check in with him every now and again, as the months went by and they were working away in the writers’ room. And Peter would say to me, “Oh man, it’s gonna be a big one.” I started to get nervous. And Gordon Smith was writing it, and I ‘d say to Gordon, “Is he telling me the truth or is he just messing with me?” And Gordon would just shake his head.

It was truth in advertising. When I read it I thought, “How are we going to do this?” It has to shoot way out in the desert, which makes everything harder — because you have to bring your own water and your own everything. You’ve got to bring everything that you’d normally find on a soundstage. But I think it was two hours door-to-door from where I stay in Albuquerque to the set, and those are those are hours that you that you don’t get back. So we wound up staying at Route 66 Casino way out on Interstate 40, which was really nice home to us for a couple of weeks, and that cut an hour out of the drive. But only an hour. We still had an hour from there to the set, and once you’re out there it was over 100 degrees and there’s tarantulas and there’s these insanely dangerous cacti, but mainly, it’s the sun and the lack of water that will just kill you out there.

At least they weren’t method acting and actually carrying heavy bags of cash for hours on end across the hot desert.

I wanted Bob to be method and drink his own pee. He’s pretty method, but he drew the line at that. But yeah, those, those prop bags of money would weigh 150 pounds. Mark Hanson, our prop master, figured out that each bag would weigh 75 pounds for a total of 150, if they were real. That’s how much $7 million in hundreds actually weighs, believe it or not. Bob wanted them pretty heavy, but not that heavy. And I think as the days progressed, the prop bags got a little lighter and a little lighter. Because it was rough.

This is an episode that seems to solidify the working relationship between Mike and Saul. How pivotal is this in setting up their new understanding?

I was so lucky to draw such a great script and the things that happen in it. What Gordon and Peter and the writers came up with, they’re going to be keystone moments throughout the whole universe between the two shows. There are these big moments, where Mike and Saul/Jimmy really kind of bond, that’s a big one. We had gone several seasons without Jimmy spending much time with Mike. We were always sad about that, but you have to go where the story takes you, and the story took these two characters away from one another for quite a number of episodes. So getting to have really concentrated scenes between these two characters, in essence get to direct a two-hander between these two characters, was a big honor for me.

Kim visiting Lalo in jail doesn’t seem like a good idea. As they were talking about Kim and Mike says to Jimmy, “Well, she’s in the game now,” there’s a lot of obvious foreshadowing there.

Yeah. No kidding. That’s the truth.

Tell me more about that shootout scene, would you say that’s the most action-packed moment we’ve seen on “Saul” so far?

There are so many beats in it and it was important, just based on my read of the script, to play the whole thing as much as possible from Saul’s point of view. Pre-shootout, shootout and then the post-shootout moments. And that made it a bit tricky, in terms of wanting to have Bob Odenkirk in every shot if possible. There are one or two shots that he’s not actually in, but I would hope at least 90% of the shots include him in it, even if he’s a little tiny character in the background. He almost gets killed and then the shooting starts and then he has to hide out. He sees another vehicle coming and then all these other vehicles need to get their tires shot out so that they’re not viable means of escape for Mike and Jimmy later. Jimmy’s own car needs to be shot, except in a way that makes it drivable — but not for long.

There were so many little moments that had to be serviced. It was huge and it was exhausting to shoot for everyone, for the crew, certainly for Bob, and all of the stuntmen who did such a wonderful job playing those bad guys, that gang of robbers. And it’s with the sun beating down on us all day long. I believe it took four and a half or five days to shoot. I don’t know that I’ve ever worked on one scene that long or that hard before, and when we finally got through it, it felt like a great weight was lifted off of us. But then we realized, “Oh my god we got the whole rest of this episode to go, there’s so much more to shoot.” It was big.

Who are those thieves? How are they connected to the Salamancas?

They are cartel-adjacent. In the teaser, you see the middle-aged gentleman who seems to be in charge of “Salamanca treasure cave” as we called it — that warehouse filled with exotic cars and then thousands of pounds of cash and the counting room and all that. He seems to be in charge of the facility, and at the end of that teaser seems to be ratting out the cousins. To who, Peter, Gordon and the writers know but I don’t think we have established that yet for the audience.

Meanwhile, Lalo in jail seems the happiest that we’ve seen him on this show. He seems to be enjoying all of this.

He is a happy go lucky so-and-so, isn’t he? He’s going to enjoy life even if he’s locked up in some crappy jail. He doesn’t let things get to him. If he wasn’t such a psychotic, motoring maniac, he be a lot of fun to hang out. You’d want to go have a cerveza with him. He’s fun and he’s got charisma and he’s got a sense of humor. And he seems to keep pretty happy-go-lucky in a very attractive way. But it’s the sort of pointless sociopathic murdering of people that is a bit off-putting. Kind of balances the scale in the other direction.

How does this set up the last two episodes of the season?

It tees things up for two killer episodes that are coming up next. Episodes 9 and 10, they’re just big and there’s so much stuff that’s going to happen coming up next. I can’t wait for audiences to see it. This show is on rails from here on out. It just goes, there’s just so much stuff going on. And these worlds really continue to collide, like the Hindenburg crashing into Lakehurst, N.J. The catastrophe keeps getting bigger and bigger, between Saul Goodman’s world and the world of the cartel and Gus Fring and Mike Ehrmantraut and Nacho Varga and Lalo Salamanca. There’s all kinds of big stuff coming up and I can’t wait for audiences to see it.

You’re back, working on the final season right now. How’s it going?

We’re plugging away. We’ve been doing video teleconferencing so that we’re having a virtual writers’ room. Peter and all the writers and myself are all joined together with the aid of internet technology and kind of hate it. But it is amazing technology, it’s not any one technology we hate, we just sort of hate having to do it in general. We’d much rather be in person, enjoying each other’s physical company. And it’s a little harder to make it work with the internet sometimes lagging, people tend to talk over each other without meaning to and staring at an iPad all day for hours on end, is making me actually fear for my eyesight.

But it’s better than not working, and we’re actually pretty productive with it, and I’m happy to be back in the room. I hate that all this crazy virus crap is going on but I’m happy to actually be in the room right now, with all this madness going on. It actually gives my life a structure it probably wouldn’t otherwise have. So I’m lucky that they wanted me back and I’m having a great time doing whatever I can do to help. I need to stress that they don’t need me, they did just fine in Season 5 without me, and I’m just happy to be back, having whatever small part I can have in the breaking of the final season.

“Better Call Saul” airs Mondays at 9 p.m. on AMC.