Part of me thinks the best thing to do is just to point to the star rating and then tell you only exactly what I knew about Shadow in the Cloud before I sat down to watch it: it's a World War II movie starring Chloë Grace Moretz as some manner of airwoman, it has a feminist bent, and it has an uncommonly correct and gratifying running time of 83 minutes. And that's 83 minutes after its none-too-short end credits scroll, mind you. In so doing, I would preserve for you exactly the same experience I had, of a very odd opening that suggests the movie is going to go in a certain direction, and it does go in that direction, just as you'd expect, only it somehow does it in a deeply shocking and loopy way, and then it continues to go in a hell of a lot of other even loopier directions.

The problem with that approach is that, before I sat down to watch Shadow in the Cloud, I had absolutely no expectations for it whatsoever, and was mostly spinning it up because that 83 minutes seemed to promise an nice way to burn off some time I had to kill and didn't want to spend it dealing with a movie that I'd need to pay attention to, or would later want to write a review of. And, well, here we are, so that part didn't pan out. So I probably really will have to go on and spoil the first surprises - no worries, there are plenty of surprises yet to come - but before I do that, just a couple more vague notes: it's an action-horror film, and it is unbelievably stupid and ludicrous but it is aware of being stupid and ludicrous, while taking a very po-faced tone: it is dumb, but it takes being dumb very seriously. And if you trust me enough to take my word on horror that's too dumb for words but is also so much fun that I have with very little hesitation given it a four-star review, maybe consider jumping ship now.

For everybody who remains, how about we get to talking about this feminist message movie about a woman trying to kill a gremlin? The kind that sabotaged planes in WWII, not the Joe Dante kind. Because that's what this is - it's basically the iconic Twilight Zone episode "Nightmare at 20,000 Feet" (the one where William Shatner thinks he sees a menacing creature on the wing of a plane), made longer and with the addition of a wild new third act. First, we get that prologue, a faux-'40s cartoon about gremlins overtly modeled on a "Private Snafu" short, only there's something terribly off about it. "Something" clearly just means "it was animated, cheaply, on computers", but the filmmakrs exaggerate things by creating some fake bad animation, adding a drop shadow to the main character that makes him look like an animation cel that's curling up off the background. It feels like something made desperately fast and artlessly, a scream of madness hiding inside banal '40s animated comedy.

After this wraps up - never telling us that gremlins will show up in the film, only raising the possibility that they might, and this hangs over the first act that otherwise does nothing to act like a horror movie at all - Moretz shows up as Maude Garrett, a woman with a stressed-out expression and a mysterious satchel of documents that she's extremely unwilling to discuss, but it's clear from her refusal to discuss them that they're important as hell. She sweeps her way onto a B-17 Flying Fortress about to depart from New Zealand on a non-combat mission, much to the irritation of the all-male crew who aren't happy about this last-minute addition to their orders, and perhaps in retaliation force her to make the trip in the isolated gun turret mounted to the belly of the plane. Here, she can hear the seven crewmembers of the Fool's Errand, as it has been nicknamed, only as staticky voices over a pair of headphones, as well as the bangs and creaks that are part of the ordinary operation of a B-17. Or, as she pretty quickly figures out, part of the work of a hideous being that's halfway between an opossum and a vampire bat, ripping parts off the plane and generally working to cause mischief. And boy, does it get pissed when it realises she's seen it.

The great majority of the film takes place in that turret, where we are locked into hearing only the little bit that Maude can hear, while everything comes in the form of close-ups and medium close-ups and we only ever look at Moretz's face or see things from the character's POV. And here's where we get to one of the most exciting things about Shadow in the Cloud, which is that it's the clearest demonstration in ages of how much a talented filmmaker can thrive from extreme limitations, such as presenting 80% of an entire feature film in a space the size of a bathtub. Based on the results, director Roseanne Liang (who also co-writes, sharing credit with Max Landis; the official story is that she's more or less rewritten his draft from top to bottom, but that has the unmistakable whiff of an agreed-upon exaggeration as a way of getting the film distanced the hell away from Max Landis) is one hell of a talented filmmaker indeed, for Shadow in the Cloud makes an out-and-out triumph of its minuscule set, both as a character study and as a thriller. In the latter capacity, of course, the film is making much out of limiting our vision and thus our knowledge of what the hell is going on, and where that gremlin is. In the former capacity, it provides a natural reason to be pressed disorientingly close to Moretz, often giving us nothing to look at but her exhausted, miserable facial expressions as the seven mostly unseen men belittle her, mock her, and make crude sexual jokes about her, sometimes not realising that she's listening in. Sometimes.

The film's minimalist approach to genre works like gangbusters, outside of the unfortunately amount of attention given to the CGI gremlin, and it's accentuated especially by two other stylistic elements. One of these is Kit Fraser's cinematography, a combination of naturalistic low-lighting with a handful of outbursts of striking primary-colored lighting in scenes that are flagged as taking place within Maude's mind's eye (notably insert shots of the male crew the first time she hears their voices over the headphones, as straight-ahead, centrally-composed singles with strong side lighting against pitch-black backgrounds), or otherwise moments that are yoked to her subjectivity. The other is Mahuia Bridgman-Cooper's extraordinary score, a synth-heavy, almost constant drone of hazy ambience that does more than any other single element of the film to ground Shadow in the Cloud in a very particular aesthetic universe: it's an '80s throwback built inside a '40s throwback. That is, we're watching a contemporary B-movie using the style of a different generation of B-movie to tell a quick and dirty single-character story that belongs to still a third generation of B-movie. The music is what most directly ties this to the '80s, but it also creates a feeling of dreamy placelessness and timelessness that covers all three periods the film is drawing from. It feels anachronistic - there's not much of any attempt to evoke "The 1940s" in any kind of recognisable way - but the anachronism feeds its grungy midnight movie energy of being in some manner of weird plane-themed nightmare.

With such a short running time to fill, having that energy is really all the film needs. It's not all the film gets - Moretz gives, genuinely, one of the best performances I've ever seen her give, in part because the character's sharp irritability and open hostility in the face of some really horrible men embraces all of the actor's strengths (almost all of Moretz's worst performances come when she's trying to play meek and vulnerable characters; here, even in the face of the gremlin, she's responding with adrenaline-fueled alertness rather than fear), in part because Liang does so much to frame the movie around her facial expressions. And there's something deeply gratifying about a film that lets its very overt social message fill in the cracks between the story rather than use it as a substitute for story. Still, the main draw here is that wild, panicky, hallucinatory feel that the colors and music and cramped space give to the film, and then the really fun things happen when the film starts to open things up, tonally if not physically. I will not say what happens, other than to mention that there's a moment of slapstick movie physics that I think either makes or breaks the film entirely, based entirely on how happy you are to be basking in the utter gonzo absurdity that Liang is spinning by that point (I was entranced by the film's fearlessness in doing something so unapologetically stupid without blatantly telegraphing it as a joke). Whatever we can say about Shadow in the Cloud, it doesn't let up, and it is petrified of being boring, so something new and ridiculous arrives at a fairly steady clip.

It's hardly a perfect movie, eventually pushing its luck too far with a final act (it manages to fit four, not counting the animated prologue, into its tiny running time, which I think is a sign of how many plates Liang is spinning) that abandons the film's strengths for a banal, abrupt finale. But who needs a perfect B-movie? Shadow in the Cloud is a wild pile-up of nonsense played with an impeccably straight face, and it beautifully showcases Liang's ability to direct the hell out of almost non-existant dramatic material. This is trash cinema through and through, but trash cinema made with love and thoughtfulness and a terrific sense of fun.