The movie that shot Ewan McGregor to stardom was, unquestionably, 1996's Trainspotting: a relentless and stylishly unhinged depiction of the depravity of heroin addiction, based on the novel by Irvine Welsh. When it came out, it seemed like a total bolt from the blue — unless you had already seen Shallow Grave.

Shallow Grave, a nasty, low-rent Scottish black comedy from 1994, is kind of a dry run for Trainspotting. It was the first collaboration between the Trainspotting trio of McGregor, director Danny Boyle, and screenwriter John Hodge. It was Boyle and Hodge's first movie, and only McGregor's second, and it certainly feels like a first film — it's edgy, nervy, eager to shock and to leave an impression, but also enjoyably flippant. It doesn't take itself too seriously.

Knowing the careers Boyle and McGregor went on to have, it's fascinating to watch now. You can see Boyle working out his jittery, hyperactive style in real time, while McGregor immediately latches on to his talent for tipping his cheeky, likable persona over the edge into darker material.

Alex (McGregor), Juliet (Kerry Fox), and David (Christopher Eccleston) are a trio of self-satisfied, cooler-than-thou roommates sharing a spacious, well-to-do apartment in Edinburgh. Alex is a motormouth journalist, Juliet a sardonic hospital doctor, and David a buttoned-up accountant. The movie opens on them interviewing candidates for the fourth room in their apartment as if the vacancy was a rare privilege; they interrogate and humiliate the poor hopefuls and then bray with laughter afterward. As if anyone could infiltrate this trio!

The successful applicant is a cool customer called Hugo (Keith Allen — Lily and Alfie's dad). Juliet, who loves to toy with her roomies' affections (she literally steps on Alex at one point) is quite taken with this terse stranger. But no sooner has he moved in than Hugo dies, naked, in his room, of an apparent drug overdose, leaving behind a suitcase with millions of pounds in cash.

The three friends decide to keep his money and dispose of the body in grisly fashion. Alex is a crime reporter and fancies that he knows the moves, although his attention to detail is lacking in one key respect, as you might be able to tell from the movie's title. This isn't the only reason their plot starts to unravel, though, as cracks in their inseparable mind-meld start to appear over who will do the dirtiest part of the deed and what should happen to the money. David becomes paranoid, Alex gets reckless, and Juliet thinks she can play both ends against the middle. They can't all be right. Meanwhile, a couple of murderous crooks are on Hugo's trail.

Shallow Grave is one of the earliest and purest artifacts of 1990s "Cool Britannia." It's flashy and brimming with energy and Tarantino-inspired grindhouse grit. It's built out of broad gestures rather than detailed character work or plotting that makes sense, but it really lands its big moments and smacks its points home. As much as the movie satirizes the callow cynicism and youthful arrogance of its three lead characters, it kind of shares them.

Shallow Grave is one of the great movies about being in your twenties, because it embodies the smug feeling of invulnerability you get among friends at that age — the sure sense that you are the coolest, funniest, and rightest people who have ever lived. (Can you tell I was 20 when I first saw it?) It's also a great movie about having roommates, and how that intense but fragile bond can break in the most disastrous way.

Fox, Eccleston, and McGregor are all superb, but it's McGregor who really carries the film's spirit — so likable yet so punchable, the cocksure dynamo who knows he'll get the last laugh. He mellowed a lot in later roles; you don't get much more chill than Obi-Wan. But even then, he never lost that wicked glint in his eye.

Shallow Grave is available to rent or buy from Apple, Prime Video, and other digital platforms