Throw in an unfocused script that features too many half-explained locations, a boggling array of alliances and counter-alliances among peripheral characters, and a primary villain almost completely devoid of charisma or subtlety, and the result ought to be a cosmic disaster.

Yet remarkably, it’s not. Guardians of the Galaxy may be a bit of a mess, but it’s an extremely good-natured mess, full of humor and even tenderness. Perhaps more surprising still, it’s the very elements that seemed most likely to ruin the film—e.g., the tree-man, the raccoon—that account for much of its improbable charm.

The giddy, picaresque space opera opens quietly in the 1980s, with a young boy visiting his cancer-stricken mother in the hospital. (Warning: This scene may prove a bit much for the kids. It may also prove a bit much for any grownups who, like me, are susceptible to heartbreaking appropriations of 10cc’s seminal “I’m Not in Love.”) Mom asks him why he’s been fighting with other boys. “They killed a little frog that didn’t do nothin’,” he tells her between tears. Moments later, after the boy has fled his mother’s deathbed and the hospital itself, an alien warship drops out of the night sky and scoops him up.

Fast forward 26 years, and we’re reintroduced to this gentle soul as an adult, played by Chris Pratt. Named Peter Quill—but trying very hard (and with very little success) to adopt the sobriquet “Starlord”—he’s now a space bandit, burgling the ruins of a desolate planet for an alien orb. Quill manages the theft, though complications ensue. No sooner does he return to civilization than he finds himself targeted by a pretty, chartreuse-hued killer named Gamora (Zoe Saldana) on the one hand, and a sentient raccoon named Rocket (voiced by Bradley Cooper) and his extraterrestrial Ent bodyguard, Groot (voiced by Vin Diesel), on the other. After tussling briefly over the orb, all four find themselves in a vast intergalactic prison, where they eventually ally themselves with an immense and irony-free bruiser named Drax (wrestler Dave Bautista). Following an elaborately entertaining prison-break, the newly minted quintet…

Well, I won’t reveal the rest of the plot, in part because I don’t think I could if I tried. Suffice to say that the alien orb is one of the half-dozen “infinity stones” with which the unfolding Marvel-verse is increasingly concerned (the Tesseract and the Aether are the two others introduced to date) and pretty much everyone in the film is trying so hard to get his or her hands on it that it might as well be the Maltese Falcon or Ark of the Covenant. Principal baddie Ronan (Lee Pace) wants the orb so that he can trade it to Thanos (a brief, performance-capture appearance by Josh Brolin) in exchange for the latter destroying the home world of his sworn enemies, the Xandarians (who count among them characters played by John C. Reilly and Glenn Close). The Collector (Benicio del Toro) wants it because he already picked up one infinity stone in Thor: The Dark World and—obviously—because he collects stuff. And Pratt’s prickly father-figure and erstwhile kidnapper, the marauder Yondu (played with blue-skinned relish by Michael Rooker), wants it because it’s worth a lot of money. Complicating matters still further, Gamora, who is the adopted daughter of Thanos, initially wants the orb, too—though whether to placate or to betray Thanos (and by extension Ronan) is unclear. She also has another adopted sister, Nebula, who’s in a similarly uncertain motivational boat.