If regret is a time machine, guilt is the key that starts the engine. This is the last lesson “Better Call Saul” leaves us with through the stations of Jimmy McGill’s acts of penance in “Saul Gone,” starting with disposing of Gene Takavic in a filthy dumpster.

Jimmy’s post-Saul Goodman identity never suited who he aspired to be; it was created by another man, Ed Galbraith, to enable him to disappear.

Once the cops find him, Jimmy casts aside the mild-mannered Cinnabon manager to resurrect the unflappable Saul Goodman, in order to play the part all great con men were born to do. That is, he’s there to figure out an angle that’ll secure the best outcome for him while screwing everyone else.

Saul calls his old nemesis Bill Oakley, a former deputy district attorney now practicing criminal defense. When Saul dangles the promise that his case will make Oakley’s career, Oakley isn’t convinced, citing the ponderous mountain of evidence against his one-time adversary. “Where do you see this ending?” Oakley asks.

“Where do I see it ending?” replies Saul. “Um . . .with me on top. Like always.”

And he would have, if not for guilt’s intervention.

“Better Call Saul” co-creator Peter Gould wrote and directed this episode, intending it to close the book on the “Gilliverse,” the nickname for the mythology Vince Gilligan began with “Breaking Bad” and continues through his feature “El Camino.”

“Saul Gone” also doubles as a meaningful examination of what justice means for a character like Jimmy McGill, who Bob Odenkirk has substantially evolved since the “Breaking Bad” episode in which Gould introduces him to this mythology.

Gould reminds us of that by returning to three memorable scenes from Jimmy’s past, augmented by passages that may have been fabricated by his guilty conscience. The first takes us back to the fifth season episode “Bad Choice Road” and the desert Saul Goodman and Mike Ehrmantraut (Jonathan Banks) traveled on foot while carrying $7 million in cash on their back. In that installment Saul is forced to drink his urine to survive. But in this version, he and Mike stumble upon a well.

Is this a detail Saul dreams up to stifle his shame or did that really happen? That’s up to us to decide. What matters is the moment when Saul persuades Mike to fantasize with him about using the money to build a time machine. He asks Mike where he’d go, and Mike says he’d go back in time to repair the mistakes that led to his criminal life, fixing his relationship with the people he cares about. Saul, on the other hand, would use it to make a sure investment with Warren Buffett that would guarantee he’d be a billionaire in the present.

“Is that it? Money?” Mike asks.

“What else?” says Saul.

“Nothing you’d change?” Mike presses. Saul doesn’t have an answer.

Jimmy’s second vision returns him to the bunker under Galbraith’s vacuum shop, where he’s hiding out with Walter White (granting one last glimpse at Bryan Cranston in that career-defining role). Posing the time machine question to Walter only earns the meth manufacturer’s ire.

“You are not talking about a time machine, which is a both real and theoretical impossibility,” Walter fumes. “You are talking about regrets.” When Jimmy asks Walter to name his greatest regret, Walter says he wishes he hadn’t walked away from Gray Matter Technologies, the company he started with his Caltech buddy Elliott Schwartz and his ex-girlfriend Gretchen, who bought him out for a few thousand dollars and went on to make millions.

Saul’s regret is low-balling Marshall Fields in a slip and fall scam he pulled. Walter is stupefied, then disgusted. “So , , , you were always like this.”

The last shameful time jump takes us to a standard delivery run Jimmy makes to his brother Chuck (Michael McKean) when he was in the full grip of his alleged electromagnetic hypersensitivity disorder. Jimmy, of course, insists on bringing Chuck everything he needs despite Chuck reminding Jimmy that he has the means to hire a gofer. But Jimmy reminds Chuck that he’d do the same for him – knowing full well that Chuck wouldn’t.

“Jimmy,” Chuck says, “If you don’t like where you’re heading, there’s no shame in going back and changing your path.”

A few moments later Chuck’s face darkens more in their already dim surroundings. “We always end up having the same conversation, don’t we?”  Then he retrieves the book he’s reading from the countertop: H.G. Wells’ “The Time Machine.”

Looking back on most of the series from the perch of these final episodes, it was plain to see that no matter what confronted him, Saul Goodman would figure out a way to wriggle free of his actions’ worst consequences.

But this doesn’t account for Jimmy’s role in all this. The tragedy of this show is in knowing that regardless of the name he goes by, the main character will always be that Midwestern screw-up driven to prove wrong anyone who doesn’t believe in him and moved to do anything for the people he loves.

Creators of terrible men like Walter White are stalked by the question of whether their antiheroes would or should die for their crimes as the end of their story approaches. But that was rarely if ever a question asked about Odenkirk’s criminal attorney. Saul was never destined to go down in a blaze of bullets. His decline was always spiritual, and steady in its progression. Death is too simple of an exit for a man like that.

Besides, some part of Jimmy probably wanted Gene Takavic to get caught. He could have remained an invisible man continuing to blend in with the black-and-white mall-scape in Omaha, Nebraska. Sure, he was recognized by another schlub who used to live in Albuquerque. But what else is Saul good for, and at, if not figuring out solutions to sticky impossible problems?

That he does before surrendering to his psychological flaw: his inability to be content with whatever success he ekes out.

Gene quickly turns from a low-stakes fraudster to a loser fleeing on foot with what remains of his life in that shoebox, only to lose it all at the bottom of that garbage bin, loose diamonds and all. Gene slithers into that receptacle and arises from it, hands up and covered in slime, as Saul Goodman.

The perfect series finale is elusive, and almost always a matter of luck instead of intention. Gould apparently knows this, which he demonstrated by striking a balance between delivering just closure for Jimmy McGill and all the men he purported to be and tying up whatever loose ends were leftover from Heisenberg’s wreckage.

Incorporating Cranston into the finale returns us to where Saul Goodman’s story began and reminds us of what he risked turning into. Bringing back McKean’s Chuck reminds us of why Jimmy’s soul became corrupt in the first place. And Mike . . .  solid, honest, devastating Mike.  Saul didn’t kill him, but he did lead him into Walter’s crosshairs.

Gould also invites back Marie Schrader, Hank’s widow (Betsy Brandt), so we can see the victim of one of Saul Goodman’s greatest crimes stare him in the face, alongside six federal law enforcement officers.

But that doesn’t faze Saul. Nor does a slew of charges carrying penalties of multiple life sentences. In Marie’s presence, Saul melodramatically presents himself as a victim, reframing the story of his first encounter with Walter and Jesse Pinkman as the start of a multi-year hostage situation. He points out that the prosecution doesn’t have to buy his story. All he needs is to win the sympathy of one juror.

This spooks the feds enough to negotiate a plea deal that whittles down the threat of dying in a miserable prison to seven and a half years to be served at the same light security facility housing Bernie Madoff.

Only when he petulantly presses his luck by offering to give up details on what happened to Howard Hamlin – solely a shot at securing a weekly pint of Bluebell mint chocolate chip ice cream –  does he find out that Kim (Rhea Seehorn) has already spilled her guts on that front, placing her own freedom in jeopardy.

Rhea Seehorn as Kim Wexler in “Better Call Saul” (Greg Lewis/AMC/Sony Pictures Television)

Kim is the only person who loved Jimmy and never tried to screw him over. And that changes the terms of the punishment he’s willing to endure.

It is uncommon for a figure like Saul Goodman, who’s neither benevolent nor entirely evil, to receive full mercy from those who wrote him into existence. Similarly Jimmy does not aim for benediction but, by the grace of Gould, receives it anyway.

When Saul Goodman arrives in that Albuquerque courtroom one last time  – invoking his magic phrase “It’s showtime” before sealing his fate – he changes his story to assume guilt for everything.

Before the court, Saul confesses to all of it, eating Kim’s sins for good measure, along with screwing over Oakley one last time. He invokes Chuck’s name and confesses to ruining the one thing Chuck lived for, practicing law, in a shot that incorporates the courtroom’s Exit sign and its irritating electrical buzz. He even takes the blame for Chuck’s suicide.

He ends by telling the judge that he doesn’t want to be referred to as Saul Goodman in the complaint. “The name’s McGill,” he says. “I’m James McGill.” Then he turns around and gives Kim a lingering, contrite look.

Nevertheless, it’s Saul Goodman’s reputation that protects Jimmy on his way to Montrose, the lonesome prison dubbed the Alcatraz of the Rockies. A fellow convict recognizes him on the bus, and soon enough everyone on board is chanting his catchphrase: “Better! Call! Saul!”

That would be enough for the finale to live up to its title, and a fitting coda to a season that started with a cascade of the luxurious objects that made Saul Goodman who he is being stripped away by the cops. Everything the criminal lawyer earned is gone, except his name.

Instead, Gould lets us know that’s not all he has. Sometime later, after Jimmy’s found a new and poetically appropriate purpose as one of the prison’s bakers, he receives a visit from his attorney: Kim Wexler.

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Kim tells Jimmy that her New Mexico bar card doesn’t have an expiration date. And in another moment that bridges “Breaking Bad” with “Better Call Saul,” they share a cigarette.

The “Breaking Bad” cigarette hid ricin, bouncing around from one hiding place to the next until finally being used to kill a greedy sociopath who deserved it. “Saul Gone” uses one to show that the bond Jimmy and Kim share remains intact; the glow of the flame that lights it, and its cherry, provides the sole golden glimmer in this black-and-white goodbye.

She marvels that he had them down to seven years, only to trade it in for 86 years.

“But with good behavior, who knows?” he says, taking another drag.

Jimmy ends up where he was always going to be, sending Kim back to freedom with this signature one-two finger gun salute – and bound to 86 years’ worth of time but unburdened of the guilt bouncing him from old regrets toward new ones.  

With that, Saul Goodman’s engrossing, poignant and beautifully tragic story is finished. And in the end, it really was all good.