When we meet Rudy (Chris Doubek), a bitter writer nursing a six-year-old book outline, he’s living in his Ford Escort and washing in his front yard. Thrown out by his long-suffering wife, Diana (Heather Kafka), Rudy is in no mood to entertain his visiting younger brother, Paul (Alex Karpovsky), a best-selling author of young-adult fiction. But later in the film, when all three converge on the Utah ski lodge where Paul is working simultaneously on his new book and Diana’s affections, Rudy discovers a gift for sabotage that’s far more satisfying than silent resentment.

Smartly written and flawlessly acted, “Lovers of Hate” is a Trojan horse, the kind of movie that begins so self-effacingly that we don’t expect any surprises. Concealing its cleverness in scenes that feel as natural as the performances — Ms. Kafka is particularly good as the unwitting pawn in a lifelong game of sibling one-upmanship — the story (by the director, Brian Poyser) approaches sex and relationships with a welcome maturity. So when Paul and Diana tumble onto a couch in urgent lust, their postcoital awkwardness is given as much attention as the act itself.

Flirting with several genres — romantic comedy, psychological thriller, stalker drama — while committing to none, “Lovers of Hate” accumulates tension in the smallest of ways. Within this sick love triangle, even something as simple as a photograph on a laptop will give you chills.

LOVERS OF HATE

Opens on Friday in Brooklyn.

Written, directed and edited by Bryan Poyser; director of photography, David Lowery; music by Kevin Bewersdorf; production design by Caroline Karlen; produced by Megan Gilbride; released by IFC Films. At the reRun Gastropub Theater, 147 Front Street, Brooklyn. Running time: 1 hour 33 minutes. This film is not rated.

WITH: Chris Doubek (Rudy), Heather Kafka (Diana), Alex Karpovsky (Paul) and Zach Green (Dexter).