Six and a half months after Renny Harlin's "The Legend of Hercules" stunk up multiplexes with its clunky, IQ-deficient ineptness, another loose big-screen treatment of the half-man/half-God warrior has arrived, this one unimaginatively directed by Brett Ratner (2011's "Tower Heist") and starring Dwayne Johnson (2013's "Pain & Gain"). Aficionados of Greek mythology will once more be left wondering why it is so difficult for filmmakers to helm an accurate adaptation of the story, though at least screenwriters Evan Spiliotopoulos (2009's "Battle for Terra") and Ryan J. Condal have an excuse: their "Hercules" is based on the character as depicted in Steve Moore's revisionist Radical Comics graphic novel "The Thracian Wars." Softened to a PG-13 rating and excising all references to Hercules' bisexuality and capricious personality found in the comics, the film nonetheless faces a major identity crisis. Too serious to work as farce and too campy to be taken seriously, the picture's tonal confusion all but cancels the entire experience out.

Hercules (Dwayne Johnson) was born a demigod, the offspring of Zeus and mortal Alcmene who faced twelve labors (among them, fighting a hydra, a giant boar and a thought-unkillable Nemean lion) in exchange for his survival from his father's vengeful mistress Hera. With those adventures behind him and the lion's hide draped across his head and back to show for it, Hercules spends his days traveling across Greece as a sort of mercenary for hire. When Princess Ergenia (Rebecca Ferguson) offers him his weight in gold to help save her kingdom from impending war, he and his weapons-wielding comrades—among them, childhood friend Autolycus (Rufus Sewell) and nephew Iolaus (Reece Ritchie)—agree. It isn't long after they have arrived in Thrace and met Ergenia's father, King Cotys (John Hurt), that it becomes clear something even more sinister is afoot on their own turf.

"Hercules" barely runs 90 minutes not including credits, a far cry from an epic summer blockbuster. Not even bothering to put up a highfalutin air of self-importance, the movie plows ahead swiftly but tediously, skipping over the series of death-defying missions in the classic story for what amounts to a fabricated semi-sequel that overhauls all that audiences might think they know about Hercules. This twist to the legend is the one and only cunning idea in Spiliotopoulos and Condal's otherwise rinky-dink script. The action relies heavily on an assortment of creatures and objects leaping at the camera (in 3D, it's cheesy, in 2D, it will be embarrassingly tacky), and when that fails Ratner falls back on dime-a-dozen battle sequences where flaming arrows fly in tandem through the air and rows of soldiers put up their shields. As is the case with so many of these sword-and-sandals actioners, there is no one in view who is developed well enough to care at all about. Deciphered by names and looks, they are given nothing to do but chew the scenery, pose as comic relief (that duty would fall to Ian McShane's fatalistic Amphiaraus), or stand in a line on both sides of Hercules and look tough, tired and pissed off.

Give it to Dwayne Johnson for retaining composure and dignity when someone of less charisma could have gotten unintentional laughs with this material (and the stringy wig he is forced to sport). In a role that Arnold Schwarzenegger would have played thirty years ago—and he kind of did, in 1982's edgier, more inventive "Conan the Barbarian"—Johnson flexes his biceps, makes the female day players swoon, and delivers tongue-in-cheek jokes one broad pun away from "Airplane!" territory. When the humor subsides long enough for him to give a would-be inspirational pep talk to his troops about victory, it's enough to put anyone's rolling eyes into an outright talespin. By the time a defining tragedy from his past is uncovered and he locates a newfound strength and drive within himself he didn't know he had ("I...AM...HERCULES!" he yells while pulling metal chains clear out of the stone floor), the film is basically over at the exact point it finally starts taking off.

"Are you the legend, or are you the truth behind the legend?" Amphiaraus queries the title hero near the end of "Hercules." Although the answer comes shortly after this question, director Brett Ratner shows little interest in genuinely exploring him as a person or a mythological figure. Instead, he has made a trivial $100-million throwaway told with a dearth of grit and way too much unconvincing CGI. Antiseptic and dreary with absolutely no dramatic pull until the final ten minutes, the film winds down just when it has located a last-gasp charge of energy. What, then, is the point? "Hercules" did right by casting Dwayne Johnson in the lead, but then lets him and the audience down. This is overpriced, distinctly unsatisfying Hollywood schlock without a trace of bite.