For alcoholics, a critical part of recovery is making amends to the people you've harmed, but for Gloria (Anne Hathaway), that part of the 12-step plan is going to be a doozy. A binge-drinking, hard-partying unemployed writer, she's already run through her boyfriend's patience and much of his available cash when she drags herself back to her small-town home, taking up residence on the floor of her parents' vacated house amid the dust bunnies. She immediately spots a friendly face in the form of Oscar (Jason Sudeikis), a grade-school pal she hasn't seen in years, but within minutes of hopping into his pickup truck she's got one more thing to apologise for: when he tells her his mother died, she apologises for not knowing, and he reminds Gloria that she went to the funeral.
Addicts are often called upon to confront their demons, but rarely in such outrageously literal terms
The damage Gloria causes can't solely be measured in blown opportunities and awkward exchanges. The ingenious premise of Nacho Vigalondo's Colossal is that Gloria is psychically linked to an enormous Godzilla-like creature who begins rampaging through Seoul after she comes home to lick her wounds. (Not too Godzilla-like, though; the production was sued by Toho before filming started.) Addicts are often called upon to confront their demons, but rarely in such outrageously literal terms. She soon gets a job at Oscar's bar and rediscovers the pleasures of simple work and regular pay, but when the front door is locked and the neon lights turned off, the two of them, along with pals Tim Blake Nelson and Austin Stowell, keep drinking ‘til dawn, and when she stumbles home, South Koreans get crushed.
Vigalondo, whose first feature, 2007's Timecrimes, used low-tech time travel to explore the guilt of extramarital lust, understands how science fiction and domestic drama can work hand in hand, but in Colossal, the pieces never quite match up. It feels more like a study for a film than a film itself. You can see what a scene is meant to be doing, and just as clearly see it fall short, as if you're gazing through an elegant blueprint to the shoddily constructed house behind it.
For a movie like Colossal to work, the quotidian drama has to be as engrossing, if not more so, than its fantastical analogue, but Vigalondo seems far more engaged by metaphoric possibilities than mundane realities. The film goes dead when it's just people talking in a room, which is far too much of the time. Hathaway indicates to the heavens, twitching and gesturing without ever getting under her character's skin, and Sudeikis is flat and bland, not the sweet guy who makes you wonder why you ever left home but the genial dullard who reminds you why you left. (Eventually, the script calls on him to do more, but he hasn't laid the groundwork that would allow the sudden turn to come off convincingly.) The movie plays as if the production spent more time designing its monsters – which, to be fair, are quite impressive, especially on an obviously modest budget – than on rounding out its flesh and blood characters.
Take out the monsters, and it would have premiered at Sundance, not Toronto
The idea behind Colossal is so inspired it's tempting to give it credit for accomplishing more than it does: surely conceptual audacity counts for something. But Vigalondo doesn't even seem engaged enough to follow his own ideas. Why, for example, is Seoul still fully inhabited after several monster attacks? Or wouldn't the population at least be replaced, Close Encounters-style, with thrill-seeking monster watchers? The script is riddled with lapses that could have been plugged with a minor adjustment or a single line. Individually, they're forgivable; collectively they amount to an affront. It's not just plot, but character, too: Vigalondo seems to lose track of his own conceit midway through, so it's Gloria to tell a story about monsters, not using monsters to enrich Gloria's story. The kaiju starts wagging its own scaly tail.
Notwithstanding its oddball premise, Colossal feels far too familiar, one more foot-dragging drama about a 30-something screwup wrestling with her darker impulses; take out the monsters, and it would have premiered at Sundance, not Toronto. Hathaway is periodically drawn to playing women with control issues, but Vigalondo never gets her to let go the way Jonathan Demme did in Rachel Getting Married. She's not a woman with a monster inside her, just a slightly clumsy beast stumbling through town, crushing people by accident and apologising as she goes.
If you would like to comment on this story or anything else you have seen on BBC Culture, head over to our Facebook page or message us on Twitter.
And if you liked this story, sign up for the weekly bbc.com features newsletter, called “If You Only Read 6 Things This Week”. A handpicked selection of stories from BBC Future, Earth, Culture, Capital, Travel and Autos, delivered to your inbox every Friday.