Title: Natural Selection

Director: Robbie Pickering

Starring: Rachael Harris, Matt O’Leary, John Diehl, Jon Gries, Gayland Williams

The darling of last year’s South By Southwest Film Festival, where it picked up seven awards, “Natural Selection” has an interesting central idea and a pair of fairly arresting lead turns, but it doesn’t convincingly dig down into its characters, and is further bogged down and hamstrung by its technical limitations. A cracked road trip in which a devoted Christian housewife jointly rescues and falls for a hedonistic, previously unknown family member, writer-director Robbie Pickering’s feature debut is an indie effort shot through with good intention, but lacking in either deft enough execution or a tonal commitment one way or another that might tip it toward an honest recommendation.

After her husband Abe (John Diehl) suffers a stroke, Linda White (Rachael Harris) discovers that, though she’s been living in abstinence due to the fact that she can’t have children and Abe professes a belief that acted upon sexual desire outside of procreation is immoral, her husband has actually been visiting a sperm bank regularly for almost 25 years. Discovering that he might have a child, Linda sets out for Florida, where she finds Abe’s 23-year-old son Raymond (Matt O’Leary) outside of Tampa, living in a filthy shack with drug paraphernalia strewn about. After convincing him she’s not a door-to-door proselytizer, and paying him $20 for his time, Linda asks if Raymond has “any hobbies, aspirations or pets.” He shoves her out of his house, but later, needing to escape a police dragnet, Raymond shows up at Linda’s hotel and submits to her desire to reunite him with the biological father he’s never known.

The mismatched pair hit the road. Raymond means to quickly ditch Linda, and take her car and money. But, somewhere between petulant and overjoyed at being pampered by her, he soon develops a certain begrudging respect. Linda, meanwhile, cut off from romantic connection for so long, finds herself opening up emotionally in ways that she hasn’t been able to with her husband.

In Linda and Raymond, Pickering has one of the main ingredients for a solid cinematic effort — two extraordinarily different characters thrown together by circumstance and forced to coexist. But he never scratches past the surface of any of the other characters — including Linda’s sister Sheila (Gayland Williams) and her high-strung brother-in-law pastor, Peter (Jon Gries, of “Napoleon Dynamite”) — and so a subplot involving pursuit by the latter comes across as sloppy and ill-conceived.

Linda and Raymond remain oil-and-water types, too. The film successfully sketches the contours of their guilt and loneliness, and there’s a potent scene where Linda and Raymond open up and share difficult truths about their respective pasts after breaking into a diner and cooking up some waffles. But “Natural Selection” requires that they ignore issues front-and-center, too, like Raymond’s drug use or Linda’s Christian devotion. These problems melt away, so caught up is the movie in the self-supposed heft and engagement of its thematic underpinnings or allegorical statement.

On a technical level, Pickering isn’t able to achieve a successful juggling of tonalities via some unifying stylistic scheme. The movie is somberly shot and dressed, but as often as not kind of droll and aimed at evoking quiet, inward laughter, mainly by way of O’Leary’s blustery injudiciousness. The script’s psychological insights and dramatic payoffs, however, just aren’t significant enough. “Natural Selection” possesses the loose framework of a more interesting film, but it’s an incomplete sketch rendered in disposable fashion.

Technical: D+

Acting: B

Story: C

Overall: C-

Written by: Brent Simon