Writer-director James Gunn's first feature film since 2006's well-received, underseen genre mash-up "Slither," "Super" gets points for being so unusual—as far as R-rated superhero movies go, this one makes 2010's "Kick-Ass" look positively conventional in comparison—but it also unsettles in a distinctly off-putting way. Sharp tonal shifts can work to a picture's benefit, or they can prove harmful, and that is where this one's individual pleasures grow murky. Played for laughs much of the time despite telling a story that is almost unremittingly sad, "Super" provides a sympathetic, if gradually unhinged, protagonist, then proceeds to put him through hell for no apparent reason other than because it can.

Diner line cook Frank D'Arbo (Rainn Wilson) can remember exactly two times in his life when he was truly happy. One was his wedding day, the other when he played a fateful part in helping the police catch a runaway bandit. Both seem like distant memories when his recovering addict wife, Sarah (Liv Tyler), falls back in with the wrong crowd and starts using drugs again. Before Frank knows it, Sarah has packed up all her clothes and fled into the arms of the smarmy Jacques (Kevin Bacon). Overcome with depression and believing himself to be a loser whom no one could possibly want, Frank decides to make it his mission to rescue Sarah. Spurred by a religious superhero called the Holy Avenger and a spunky comics shop clerk named Libby (Ellen Page) who wonders why no one in the real world has ever put on a costume and fought crime, Frank does just that. His brand of justice on anyone he deems harmful to society—drug dealers, thieves, child molesters, line-butters—is swift and violent, usually involving a pipe wrench that he uses to beat up the bad guys. His secret persona makes the news, and so, too, does Libby, who thrusts herself into the part of sidekick Bolty yet can't quite stop herself from falling for him. Together, they edge closer to their target: Jacques' compound, where a strung-out Sarah is being kept.

"Super" imbues the narrative with a top-notch soundtrack of catchy indie artists, and writer-director James Gunn has nothing if not a strong auteur's vision. Rainn Wilson (2011's "Peep World") gives the best performance thus far in his career as the lonely, downtrodden Frank, effectively going for pathos even when the film itself is trying too hard for laughs that would be better-suited for something frothier. For her part, Ellen Page (2010's "Inception") is fearless as hot, bubbly nerd Libby, a young woman with a healthy sexual appetite and an unanticipated violent streak. At a certain point, however, things get so bleak that it tarnishes the good will previously built up. One character's demise is just about unforgivable, made all the worse by the suggestion, whether intentional or not, that their life was less valuable than that of Sarah, who insensitively staggers through the film using people and then discarding them like trash—not exactly the most virtuous of souls worth saving. And then there's poor Frank, well-meaning and earnest, if not exactly innocent considering the amount of people he kills along the way. His journey is intended to be one of self-discovery, but director Gunn gives him just about the most half-hearted, grim victory imaginable. The viewer is left wondering what he's really gained, and why it was worth bothering to care about him at all. The movie doesn't.