“I am not going to forget about you, Lawrence,” Caroline (Paige Turco) says with the absolute certainty of youth in the prologue to Eva Aridjis’s film “The Favor,” which opens today at Quad Cinemas. But as is so often the case with first love, Caroline’s declaration proves unreliable. With high school at an end and the greener pastures of college beckoning, Caroline leaves Lawrence (Frank Wood) behind in Bayonne, N.J., the town in which the two teenagers fell for one another. Separated by geography, they soon grow apart.

Fast-forward to the present day, and the Lawrence we are reintroduced to is 43 years old, still in Bayonne, and single. A balding, circumspect photographer who lives alone with his dog, he could be the middle-age poster boy for failing to move on. But when Caroline unexpectedly returns to New Jersey from the ashes of an abusive relationship that has yielded a 16-year-old son and ended in divorce, Lawrence’s self-mothballing seems like it might not have been such a bad idea after all. Out on a date, the couple generates a surprising amount of chemistry. They aren’t picking up where they left off by any means, but their future has arguably returned to the same level of brightness it had during that moment, decades ago, when Caroline made her false promise to keep Lawrence alive in her heart.

Fate, of course, has other plans. Caroline’s sudden accidental death leaves Lawrence more bereft than ever. It also leaves her son Johnny (Ryan Donowho) an orphan. Lawrence’s grief spawns a compulsion to take care of the sullen and troubled boy. Unlike his all-too-briefly rekindled relationship with Caroline, the personal chemistry that Lawrence creates with Johnny is highly volatile. Johnny’s realistically portrayed, sad, and disturbing compulsion to screw up everything he does and keep at arm’s length a community of people tasked with helping and nurturing him is formidable.

Ms. Aridjis uses this unsparingly austere and, frankly, rather spasmodically plotted drama to mount a precise exploration of the healing power of letting down one’s guard. Both Johnny and Lawrence tend to bite the hands that would emotionally feed them and aid their respective movements toward a better understanding of themselves, but the extent of their individual psychic damage, and the hardship of living with grief and loss, are palpable and genuine. Mr. Wood’s measured delivery is particularly well matched to Ms. Aridjis’s script, and his performance sustains an engaging vulnerability throughout.

“The Favor,” which was shot on a shoestring on location in Bayonne, is Ms. Aridjis’s first narrative feature. Though it profits from an egalitarian third-person narrative distance — born, one suspects, of the filmmaker’s previous documentary experience — there are times when the film’s ceaselessly even flow could have benefited from a few more waves and a few less ripples. “The Favor” is also somewhat overburdened with some preposterously telegraphed plot-point punches. A stern reminder from Lawrence about not letting his dog out of the house, for instance, is as good as a death warrant for the poor pooch. But the film’s generally graceful feel for real-world, small-scale tragedy is memorable, and it is a promising debut for a filmmaker with something to say, even as she continues to find the best way to say it.