Thirteen years after his debut 'For Those in Peril,' Scottish director Paul Wright reunites with that film's star for a similarly intense, solemn sophomore feature.

Back in 2013, actor George MacKay and director Paul Wright paired up for “For Those in Peril,” an atmospheric study of youthful alienation, trauma and psychological collapse in small-town Scotland that sealed both men’s place on the U.K. industry “ones to watch” list. Since then, MacKay’s career has gone from strength to strength, while Wright has made just one film in the interim — 2017’s archival doc “Arcadia.” It speaks to MacKay’s continued commitment to challenging British independent fare that he returns for Wright’s long-awaited second narrative feature. Both his stardom and his fearless approach are assets to “Mission,” an atmospheric study of slightly less youthful alienation, trauma and psychological collapse that confirms the director’s stylistic vigor and seriousness of purpose as a storyteller.

It doesn’t necessarily advance them, however. Uncompromisingly downbeat in its portrayal of an aimless Scottish service worker searching not just for a purpose in life, but a reason to live at all, “Mission” impresses with its abrasive intensity of mood, enforced through jagged editing rhythms and dreamily disorienting archival inserts — signalling a troubled mind plagued by intrusive thoughts. In subject, ambience and form, the new film does feel heavily bound to its maker’s past work — including his BAFTA-winning 2010 short “Until the River Runs Red” — minus the mythic overtones of his first feature. Wright’s filmmaking remains arresting, if not altogether surprising; “Mission” will count on MacKay’s profile to attract distributor interest following its competition premiere in Edinburgh, but it’s still no easy sell to audiences.

With jittery body language and an unnervingly directionless gaze, MacKay immediately conveys the anxious unrest of his character Dylan, even before his interior monologue clarifies the degree of his inner torment: “When I was seven, I died for four minutes,” he says in voiceover, alluding to a formative childhood accident. “I’ve spent my life wishing I could feel that way again.” Certainly, Dylan appears to live more in the past than the present, an impression assisted by editors Michael Aaglund and Jen Mackie, who constantly slice through proceedings with oblique, stream-of-consciousness flashes of home-movie memory, shot on hazy, grainy video stock.

The bulk of these memories are connected to Dylan’s older sister Claire, from whom he was once inseparable; played as an adult by Rosy McEwen (“Blue Jean”), she’s now present largely as a weary, defeated voice on the other end of the phone, at a loss as to how to help her brother through another episode. It’s left to the audience to infer exactly what has transpired between them, but largely through omission, Wright’s script effectively articulates the burden of mental illness on family members. Dylan’s friends, meanwhile, are few to none; Becky (Emma Naomi), a kindly colleague at the upmarket hotel where he works as a waiter, humors him, but it’s painfully clear that their interactions mean more to him than they do to her.

Becky, in fact, is the only thing getting him through a job he can’t bear. At a performance review meeting with the hotel’s smarmy CEO James (Emun Elliott), he finally admits that he doesn’t feel like himself in the workplace, and abruptly walks — though he can’t quite quit hanging around the place, missing what scant human connection he once had. After he decisively gives himself one week to find a reason to continue living, his behavior spirals into more extreme actions: stealing and freeing a monkey from the zoo, aggressively confronting strangers, participating in BDSM sex. These are depicted in varyingly surreal vignettes, to the point that it becomes hard to separate Dylan’s everyday and fantasy lives; Dario Swade’s fuzzily layered, industrially inflected sound design amplifies the claustrophobic confusion, as does DP Nick Cooke’s nervily handheld lensing, heavy on clammy closeups.

If this all amounts to a tough sit, MacKay’s natural vulnerability as a performer offers a kind of lifeline to viewers, even as Dylan’s behavior grows ever more erratic and offputting: The actor, often seemingly hunched over with the sheer agony of his character’s interior wounds, is easy to care about when much else here is hard to parse. Sympathetic but gutsy in his embrace of a character’s unflattering damage, he’s a vital, humanizing ally to Wright’s abrasive style of portraiture; one hopes they collaborate again, and sooner.