Richard is a bit of a hero among his South Dublin peers. Affable, convivial, star of the rugby team, He oozes style, sophistication and, above all else, class. Upper middle class, to be precise. The girls within his realm adore his confident lustre. The boys look up to him as a paragon of early adulthood social supremacy. There's a hint of existential burdens but this only adds to Richard's magnetism and mystique - that is, until events at a local house party turn ugly.

Director Lenny Abrahamson has been tacitly charting the outsiders in Irish society since his 2004 debut, Adam & Paul, which documented a day in the lives of two junkies attempting to score smack on the streets of Dublin. The despairing plight of the hapless duo was augmented by moments of physical comedy, Vaudevillian in execution, reimagining Beckett's Vladimir and Estragon through the prism of torpid drug addiction. Abrahamson followed this with the beautifully measured character study Garage (2007) which retained the comedic physicality yet dislocated it in the form of Josie, the innocent small-town misfit whose developmental difficulties prevent him from imagining the consequences of his ostensibly harmless actions. But the comedy is well and truly over and the dislocation entirely existential with What Richard Did, which again examines an oft-ignored strata of Irish society – this time Dublin's wealthy middle classes.

The stark fiscal infidelities of the recession have had little effect on Richard's world. Indeed, the Celtic Tiger is alive, well and positively purring in this vision of a moneyed, suburban idyll. But gradually, Abrahamson's nuanced direction, so tightly knit as to be asphyxiating, retreats from the bourgeois strata of society into an interior world, eschewing moral outrage or trite class denouements in favour of focusing upon Richard's burgeoning jealousies and eventual mental isolation. The film becomes Richard, his thoughts an abstract centre point as he grapples with potential recriminations as much as, or even more so, than the guilt he feels for his actions.

Larry Clark's Bully (2001), also based on a true event, adapted a similarly paced - albeit considerably more prurient - look at adolescent violence, but Clark's nefarious teens have little in common with Abrahamson's privileged youngsters. We see them boozing and shagging in the local park, but their behaviour is underpinned by a moral compass whose axis is only turned by Richard's actions. Abrahamson cleverly posits the character of Richard in such a fashion that it becomes impossible for the viewer to sustain their first impression of him. The beginning, straightforward and traditional in presentation, encourages us to see Richard as this handsome, winning jock. Moreover, it's clear that Richard believes this as well; he believes his own bullshit. But as the story develops, this view of Richard becomes harder to hold on to for himself, his friends and the viewer. He grows peripheral to his own social category, to his family, ultimately becoming an unfathomable creation. There is no character development in What Richard Did – the change is in us as we watch him.

The second half becomes so concentrated on its own intensity that this acute character study turns to entropy. The movie is coy about its position from the off, but Abrahamson's attempt to embrace an ambiguous viewpoint ultimately feels hesitant and indecisive, his work's emotional core usurped by aesthetic uncertainty.

Perhaps such solipsism is inevitable with a title character who wages the majority of his battles with himself. Jack Reynor's performance as Richard is remarkable yet not confined to moody, alpha-male brooding. There's an unmistakable chemistry between him and his off-on girlfriend Lara (Róisín Murphy) and Reynor effortlessly infuses Richard's natural leadership qualities among his peers with an ebullient charm. Abrahamson spent eight months workshopping with his youthful cast, an approach which massively contributes to the picture's unadorned feel, further tracked by shades of Bergman. In one memorable scene, Richard temporarily loses his tenuous grip on sanity while seeking sanctuary in the family's beach house, under orders from his Scandinavian father (Lars Mikkelsen).

While it may be some time before Lenny Abrahamson muscles up to his cinematic progenitors, it is within this tradition of Euroexistential angst that What Richard Did primarily belongs. And while the director may slightly falter with the pacing, he excels with his spare, minimalist approach to filmmaking, effortlessly interchanging blatant details with latent minutiae amid the gradual unravelling of terrible events. There are no moral pronouncements here, no social commentary exposés – just a bunch of teenagers struggling with everyday fears, insecurities and jealousies and prone to appalling lapses in judgement. As Richard knows all too well, it's incredibly difficult to always do the right thing.