To viewers of a certain age, Danny Boyle’s Trainspotting offered a transporting hit of Cool Britannia when it was released back in the summer of 1996. The film’s unforgettable sights and sounds included a soundtrack built on the backs of bands that were new to this listener—from Blur to Primal Scream to Pulp and Underworld—along with artists whose work felt new again, from Brian Eno to Iggy Pop.

So let me say this straight off: Neither Boyle’s sequel nor its accompanying soundtrack come nearly as packed with surprises. Boyle and screenwriter John Hodge’s adaptation of Irvine Welsh’s 1993 novel masterfully mixed humor and pathos in its hard-hitting look at a group of young junkies in Edinburgh, and any film that tried to replicate its successes was never going to recapture the same highs—the main reason all parties involved resisted relapsing for so long. And while the Prodigy may be a trailblazing electronic music act, and though their remix of Iggy Pop’s “Lust for Life”—the 1977 song inspired by Pop’s life as a heroin addict that served as Trainspotting’s theme—is certainly interesting, it still stands as a rather unnecessary redo.

But as much as I find myself questioning the need to revisit Mark Renton (Ewan McGregor), Sick Boy (Jonny Lee Miller), Spud (Ewen Bremner) and Begbie (Robert Carlyle) more than 20 years after cringing through their freewheeling, freebasing, toilet-diving exploits, I still got a sadistically nostalgic charge from peeking through my fingers at the returning group of misfits, who have been separated since Renton betrayed his friends by running off with (most of) their money, a huge haul they nabbed during a climactic drug deal.

In fact, when we first see the now 46-year-old, shaggy-haired Renton, he’s still running, only he’s traded his old habit of fleeing from authority figures for jogging on a treadmill, a metaphor for being stuck in place if ever there was one. He can’t run forever though, so a small heart attack and a stent later, he boards a plane in Amsterdam—where he’s spent the past two decades settling down and becoming a health nut—and flies back to Edinburgh to look up his old friends, beginning with Spud, the only one who still struggles with a smack addiction.

While Renton may look as good as he did as a youth (he is played by McGregor, after all, who’s become quite the star since appearing in the ’96 original), the still-meek Spud looks far worse; a bald spot now crowns his skeletal head like a monk’s tonsure, while his sunken eyes have the haunted look of a man who’s seen too much. Separated from his girlfriend and son, Gail (a criminally underused Shirley Henderson) and Fergus (Kyle Fitzpatrick), the lifelong loser has become suicidal.

I’ll note here that as depressing as the film can be, it nevertheless contains much of the humor that likewise cut the drug-induced drama of Boyle and returning screenwriter Hodge’s original. When Spud attempts to suffocate himself by placing a bag over his head, he’s interrupted by Renton’s surprise visit, in a scene that’s as sickly funny as the ’96 picture’s gag involving explosive diarrhea. Surprisingly, Spud also ends up becoming the film’s melancholic voice, replacing Renton as an accidental narrator when he discovers a new addiction: the power of the written word.

While Spud sets down his unexpected path toward recovery, Renton catches up with Sick Boy, the lifelong best friend he double-crossed. Now going by his more respectable given name, Simon, the still platinum-haired schemer has traded shooting heroin for a more upscale habit, snorting coke, which he funds through an extortion business he runs with his girlfriend Veronika (26-year-old Bulgarian newcomer Anjela Nedyalkova), a former prostitute he secretly records from adjacent hotel rooms as she “pegs” wealthy family men. After a rather painful reunion involving smashed pint glasses and broken pool cues at the loss-making pub Simon took over from his father, Veronika observes in her subtitled native tongue that Simon and Renton are “clearly still in love with each other,” before adding that they should “just get naked and fuck.” The palpable attraction between Renton and his old pal’s girl might preclude this bromance from ever taking place, however, even as this potential affair is deemed ill-advised by Renton’s old flame Diane (the returning Kelly Macdonald), who now practices law.

On the other side of the law is Begbie, who has just broken out of prison and is seeking murderous revenge against Renton. If there’s one real misstep in this picture—spun out of a few story ideas from Porno, Welsh’s not-terribly-well-regarded 2002 follow-up novel—it’s turning Begbie into a slasher movie-style boogeyman. Nevertheless, Boyle and cinematographer Anthony Dod Mantle (who both collected Oscars for 2008’s Slumdog Millionaire) have fun presenting these latter passages as what I can only describe as an off-the-rails homage to the climactic moments of Ridley Scott’s Blade Runner, a 1982 science fiction classic that’s also receiving a long overdue and perhaps unnecessary sequel later this year.

And while this film shares part of its name with another sci-fi picture with T2 in its title that travels back in time, it doesn’t quite reimagine and refocus its source as successfully as James Cameron’s 1991 sequel to The Terminator did. But in its own funny, depressing way, it ends up being a killer film about aging.

T2 Trainspotting ***

Starring Ewan McGregor, Jonny Lee Miller, Ewen Bremner, Robert Carlyle, Anjela Nedyalkova, Shirley Henderson, Kelly Macdonald, Scot Greenan, James Cosmo, Ben Skelton, Logan Gillies, Aiden Haggarty, Daniel Smith, Elijah Wolf, Hamish Haggerty, Daniel Jackson, Connor McIndoe, James McElvar, John Bell, Christopher Mullen, Kyle Fitzpatrick, Charlie Hardie and Irvine Welsh. Directed by Danny Boyle. Written by John Hodge, based on the books Porno and Trainspotting by Welsh. At Boston Common, Coolidge Corner and Kendall Square.