“You need to put this behind you, start fresh, and move on,” Joe MacMillan tells ex-lover Cameron Howe early in the fourth and final season of Halt and Catch Fire, right after she’s just suffered a major career setback.

“It’s not that easy for me,” Cameron laments.

For Joe, starting over from scratch has always been simple. As Cameron describes him in a less-kind moment, “He’s empty and he just becomes whatever circumstance needs him to be.” Though Halt has many fascinating characters, it seems to take the greatest inspiration from Joe, if only because the AMC drama shares his gift for rapid, stunning reinvention — including the way it’s transformed from a mediocre Quality Drama knock-off into one of the very best examples of the genuine article on television.

When it debuted, Halt was the meandering story of an ’80s Don Draper type (Joe, played by Lee Pace) bulldozing a Texas electronics company into building its own IBM clone — not exactly the stuff of which either dreams or great TV shows are made. By the end of its first season, it found focus in part by revealing Joe’s plan to be exactly the uninspiring cash grab that it seemed, and by bringing Joe, Cameron (Mackenzie Davis), and engineer spouses Gordon (Scoot McNairy) and Donna Clark (Kerry Bishé) onto the same team together. It kept transforming from there. Season two pushed the women to the forefront, while shifting the arena from personal computers (to quote Joe, “the thing that gets us to the thing”) to the early days of the internet (“the thing” itself). Season three moved all the characters out to Silicon Valley, with Joe making and losing a fortune on an idea he stole from Gordon, and Cameron and Donna’s partnership falling apart in a dispute over creative purity versus business reality.

Season three concluded with a time jump that brings these concluding episodes into the early ’90s, as the online world begins to more closely resemble the one we know(*): the Mosaic browser is the first to incorporate graphics, and Joe is amused to discover a website that just features a webcam image of a University of Cambridge computer lab’s coffee pot.

(*) I’m old enough to clearly remember both the era depicted at the start of the series and the one in this final season, yet as soon as Gordon got a look at Mosaic, or a party at Donna’s house was accompanied by Hole’s “Doll Parts,” my college brain kicked in and I thought, “How modern the show seems all of a sudden!” (Really, we can just shorten this whole paragraph to its first two words.)

Yet the biggest change of this new season (I’ve seen the first three episodes, two of which will air Saturday night at 9 & 10) isn’t the date, the clothes, the music, or even really the technology, which is only a more advanced version of what Cameron and Donna were working on throughout the middle seasons. Rather, the most striking difference is how the series’ alliances, and sympathies, have shifted yet again, so that characters who once justifiably despised each other are now the closest of friends, and vice versa, while Donna — long the show’s most sensible good-hearted regular — is now somehow, convincingly, the closest thing we have to a villain.

Halt in its broadest sense is about technology and the ways its advancement has affected us, but at its heart it’s simply about how people change, regardless of what sort of graphic interface or transfer protocol they’re using. Across its run, the show’s writers and its marvelous cast — also including Toby Huss as the charming (and allegedly retired) salesman John Bosworth, Annabeth Gish as Bos’s wife and Donna’s partner Diane Gould, and in the final season, Kathryn Newton and Susanna Skaggs as Donna and Gordon’s now-teenage daughters Joanie and Haley — have carefully monitored each emotional beat of the characters’ lives so that it never feels like a soapy twist when partners become rivals, but like a natural result of what each person has seen and done. Much of Saturday’s second episode is taken up by a long phone call between two characters who at an earlier point in the series had absolutely no reason to speak with one another, but it feels entirely earned, and is a beautiful reminder of how even a relatively primitive communication form like a landline phone can create just as profound a connection as the stuff that Gordon and Donna and others are working on this season.