Rachel Griffiths has been so egregiously underused on the big screen in recent years that her mere presence in a leading role is reason enough to commend “Mammal.” That Irish writer-director Rebecca Daly’s film proves as quietly, uncompromisingly complicated as the actress it showcases makes it worthy of celebration. An elliptical essay in withheld grief and reluctant desire, “Mammal” finds an improbable partner for Griffiths’ peacable loner in 22-year-old livewire Barry Keoghan’s bristling delinquent; their ambiguously sensual attraction is one of several unarticulated emotional currents coursing through a story that resists obvious psychological cues at every turn. Some viewers may feel frozen out by this piercingly performed enigma, though discerning arthouse distribs should be intrigued; the Sundance Channel, meanwhile, will secure it an audience in several non-U.S. territories.
Daly’s 2011 directorial debut, the auspicious, Cannes-selected somnambulist thriller “The Other Side of Sleep,” established the filmmaker’s affinity for coolly passive puzzle narratives fronted by female characters who encourage some scrutiny beneath the surface. “Mammal” fits the same description, while exchanging the previous film’s woozy genre flirtations for more sober kitchen-sink styling. It is, by fine degrees, the more guardedly accessible work, though not one to converse readily with its audience: What happens from one scene to the next is easy enough to determine, though the fractured personal motivations underpinning the action demand both assembly and argument.
In countenance and demeanor, then, protagonist Margaret Brady (Griffiths) is very much of a piece with the film around her. A fortysomething divorcee living in a featureless, pebble-dashed purgatory of outer Dublin, she appears to have expressly compartmentalized her life to entail the least possible amount of human friction. Running a charity shop while barely speaking to her co-workers, and dispassionately filling the second bedroom in her boxy row house with passing lodgers, she protects the secrets of her past without even seeming especially possessive of them; hers is a life lived calmly but obstinately in the present tense. In the film’s most pointed — and visually alluring — symbolic flourish, she only appears truly content during her daily swims at the municipal pool; coupled with Marco Vermaas’s elegantly amplified sound design, Lennart Verstegen’s sharp underwater lensing, effectively presents its white-tiled depths as a kind of therapeutic netherworld.
From what, exactly, is Margaret — whose very accent, an Irish-Antipodean hybrid glancingly acknowledged in the script, defies a self-evident backstory — shielding herself? Our first clue comes with an uninvited visit from her ex-husband Matt (Michael McElhatton), who informs her that their 18-year-old son Patrick has gone missing. If the news doesn’t trigger the expected flurry of maternal panic, that’s because Margaret forsook motherhood many years before, leaving her infant son in the exclusive care of his father. Coincidentally or otherwise, however, a nurturing impulse is aroused within her when she encounters Joe (Keoghan), a teenage bruiser whom she patches up after finding him beaten senseless outside her shop. Despite his feral skittishness in response to her kindness, she offers him the temporary use of her spare room; he cautiously accepts.
As delicately drawn by Daly and co-writer Glenn Montgomery, the nervous, mutually tip-toed bond that reveals itself between Margaret and Joe runs counter to the luridly melodramatic lines threatened by the premise: The characters seem as tremulously uncertain as the audience as to whether their relationship is one between a surrogate mother and son, or whether they seek a more carnal form of human contact in each other. Griffiths and Keoghan share a brittle, inquisitive chemistry that makes either outcome seem both wholly intuitive and potentially catastrophic; the stern serenity of Daly’s filmmaking, with its patiently observant camerawork and minimal scoring, thankfully doesn’t rush viewers to judgment.
Keoghan impressed last year in a similarly taciturn part in festival curio “Norfolk,” and builds on his range here, developing a distinctive physical language for Joe that is half highly mannered swagger, half involuntary animalism: In many ways, he seems as slinky and ragged as the stray cats that flock to Margaret’s backyard for feeding. Relieved of the over-instructive writing she handled like a pro on TV’s “Brothers and Sisters,” Griffiths luxuriates in her character’s fascinating inexactitude, suggesting volumes with a sudden half-smile or a sharply refocused gaze. It’s a performance that movingly registers a resigned state of mourning, though the possible undertow of her grief — for her son, for herself or for something entirely less tangible — shifts with her expression. The precise audience for “Mammal” may be indeterminate, though one hopes it includes at least a few casting directors with a keen eye for fresh faces — as well as the ones they’ve too long taken for granted.