After you’ve seen The Shape of Water come back and listen to our Spoiler Special.

The opening shot of The Shape of Water, director Guillermo del Toro’s sci-fi–tinged romantic thriller about the love between a mute cleaning woman and a mysterious river creature, achieves a haunting beauty that the rest of this ambitious but slightly strained parable never quite matches. The camera tracks slowly down the hallway of an apartment building filled to the ceiling with greenish, glowing water. The effect is eerie and apocalyptic, reminiscent of the artist Gregory Crewdson’s “Twilight” photo that showed a woman lying on her back atop an inexplicable flood in her suburban living room. In voiceover, Richard Jenkins—who, we’ll soon learn, plays the cleaning woman’s closeted gay next-door neighbor—explicitly identifies the story we’re about to hear as a fairy tale, with Elisa Esposito, Sally Hawkins’ silent heroine, as its princess. She’s seen floating in the fetal position in the water that fills her apartment, but is she dead? Under a magic spell of some kind? Or merely dreaming?

The latter interpretation seems the most likely as that lyrical first shot ends and we cut to Elisa, dry and asleep in her own bed, about to start another workday at the top-secret military facility where she mops floors.

We’re in Baltimore in 1962, at the height of the Cold War arms race, and Elisa along with her fellow custodian and friend Delilah (Octavia Spencer), know enough to keep their noses out of whatever murky deeds the scientists and bureaucrats at their workplace are up to. But one day a hardhearted government agent (Michael Shannon) wheels in a tank containing a beast kidnapped from the Amazon—a vaguely hominid fish-man, played by longtime del Toro collaborator Doug Jones in an elegantly designed full-body suit—and Elisa immediately feels drawn to the isolated and mistreated creature. He’s the only one of his kind ever to have been captured by humans and possibly the only one still in existence. (The enigmas swirling around this creature are perhaps a little too dense; over two hours we barely learn more about this gilled being’s habits and history than we knew upon first glimpsing his solemn, scaly face.)

The scenes between the lovelorn Elisa and her piscine paramour sometimes attain the magical heights of what’s still del Toro’s masterpiece, Pan’s Labyrinth.

After secretly befriending the river beast—she brings him hard-boiled eggs, plays him Glenn Miller records, and touches his webbed hand through the glass pane that separates them—Elisa learns that Shannon’s loathsome G-man is planning to have the creature vivisected, both so that government scientists can collect valuable secrets about his biology and so that the Soviets, who have now gotten wind of his existence, don’t get their hands on him first. A sympathetic doctor on the research team (Michael Stuhlbarg), who’s hiding his own secrets, decides to help Elisa in her scheme to smuggle the beast out of the facility—but once the creature is hiding out in her bathtub, where the two of them engage in some nongraphic but frankly erotic interspecies sex, he’s exposed to a whole new range of dangers.

The Shape of Water stacks the moral deck pretty hard in favor of its good characters—a lonely mute woman, a laid-off secretly gay man, a black woman in a miserable marriage, and a persecuted half-man, half-fish—and against its overdrawn bad guy, the sadistic WWII vet played by Shannon. For example, in case we weren’t sufficiently aware of the Shannon character’s moral rot, he’s given a pair of severed and then reattached fingers that are gradually turning gangrenous. There are moments, especially in the middle section, when the whimsy feels forced and the political allegory too blatant (in between scenes of Shannon torturing the river creature with a cattle prod, news footage of cops beating civil-rights protesters play out on nearby TV screens). But the scenes between the lovelorn Elisa and her piscine paramour sometimes attain the magical heights of what’s still del Toro’s masterpiece, Pan’s Labyrinth.

Like the archetypal fairy tale it is, The Shape of Water takes few unexpected twists. There’s a fair share of gory violence and a few unsettling bursts of body horror (including a trigger warning–worthy scene with an unfortunate housecat) but little real suspense. Even if you’re not transported by every minute of the film’s story, though, del Toro creates such a sumptuous visual world that it’s impossible to take your eyes off the screen. Teal green is the dominant color, giving even the scenes on dry land an underwater quality, but there’s also an impressive palette of sickly pastels (to indicate the insipidity of the Shannon character’s suburban domestic life), splashes of theater-curtain–red blood, and in one scene, a slow, thrilling shift from color to black-and-white, introducing a dream sequence that evokes the classic Hollywood movies del Toro loves to reference. The last scene returns to the same dreamlike underwater space where the movie began, this time to suggest not the main character’s isolation but her ecstatic commingling with her amphibian lover. Even if the story that came before was sometimes landlocked, the image of their conjoined bodies sinking into this enchanted realm is enough to send you out of the theater floating.