Tattooed on his shoulder blade and later being done (by Ben Thompsett) onto her buttocks, the words Nina Forever actually refer to the third party. On a seaside curve clearly marked dangerous, twenty-eight-year-old Nina Eliot (Fiona O’Shaughnessy) crashes her Honda cycle in 2013 and gives up the ghost.

Not long thereafter, a virgin nine years younger with no apparent family, Holly (Abigail Hardingham) is “a bit vanilla” for beau David (Javan Hirst), who gently drops her. To finance paramedic classes, she is a checkout girl at a dead-end suburban mall and eyes stock boy coworker Robert (Cian Barry), a failure at suicide, clumsy and removed in grief over that late title girlfriend.

In no screen- or real-time at all, the two quick young people are going at it in his apartment, smashing wine goblets, ripping off clothes, falling into bed. But as she is about to lose, or already in the very throes of losing, her innocence, dead mangled and bloody Nina shows up, interfering with, participating in, or commenting on their lovemaking.

This is, of course, disconcerting and distracting, to say nothing of her blood -- symbolic as well of the younger woman’s deflowering -- soaked all over the sheets and down into the mattress and finger-trailed on Rob’s chest.

A “cinematic bloody Valentine . . . love song to sadness” to be released February 12, writer-director brothers Ben and Chris Blaine’s feature-début ninety-eight minutes is not the straight traditional horror gore one might expect. There are, granted, echoes of awful After.Life, and in the previous inexperience and repression of Holly and the morbid state of mind of Rob, of spot-on Repulsion and overpraised Black Swan, but redeeming grace comes from the decided dark humor in situation, incident -- sheets carted to Wash Tub Laundromat and rubbish bins, an emphasized parked Honda cycle, an uncomfortable bus passenger (Richard Sandling) -- and especially in the waspish whimsical remarks of glassy-eyed returned Nina, though her sexy whispers are teasingly hard to catch. Think Dona Flor and Her Two Husbands or, those of a certain age, of the Topper franchise.

Rob still visits his dead ex’s parents Dan and Sally (David Troughton, Elizabeth Elvin), equally mourning their only child but more stuff upper lipped until the father loses it and lashes out at their never made it to son-in-law’s indulgence in self-pity. It is, however, going rather far to consider the story -- as, encouraged by the filmmakers, some have -- as one of missing someone for the wrong reasons and scarred healing after great loss.

There is too much text messaging, even if projected unobtrusively, and some unnecessary pseudo-kinkiness for public consumption -- metal fonts lugged along on vacation escape to body-print obscenities -- but on the whole there is, surprisingly, a lot of sly good fun. Rob tries to distance the dead returnee by insisting that he has broken up with her and that Holly is now the flame of his life. (SPOILER ALERT) But the suggested, lesbian-tinged, end-twist is that the return is the result of, and is enabled by, Holly’s energy and mental state, which attract Nina, and that Rob is the one to be shut out. Certainly, Holly appears unable to find fulfillment with another male, such as awkward nebbish classmate Josh (Sean Verey).

Relationships are difficult. Their component human beings generally tote along individual baggage. At times it works, at times it does not. “Forever” is an eternity, and there will be snobbish sophisticates simply unwilling to sit still so long. Others will have, not shudders or chills, but their laughs.

(Released by Epic Pictures and rated “R” for strong sexual content, nudity, bloody images and language.)