Writer-director Marielle Heller is swinging for the fences and beyond with this fantasy-satire adapted from the 2021 novel by Rachel Yoder, but it shifts away from half-hearted body-horror and allows its feral growl to become a purr of earnest assent to bland ideas of earth-mother solidarity.

Amy Adams gives what could be the biggest and most ambitious performance of her professional career in the lead and she is always very good. She plays a woman who’s been talked into abandoning her artistic career by her husband to be a stay-at-home mom to their lively little boy. Finding herself descending ever deeper into boredom, depression and secret snarling rage she also starts to discover weird tufts of body-hair and realises she is turning into a dog. Scoot McNairy is robust and plausible as her husband, and there is a nice cameo from Jessica Harper as the local librarian Norma, who shrewdly sees in our heroine’s eyes her pain and potential inner strength.

The straightforward, realistic, non-dog-fantasy part of the film is excellent on how stressful and terrifying unsupported parenthood can be. But the silly dog scenes? The freaky look in the eye, the sudden nose-twitching sense of smell, the hunger for meat, the need to gallop in full doggy transformation to kill things under cover of night? None of this is properly scary or properly funny because the film shrinks from the transgressive extreme; even Adams’s (well performed) breakdown in a restaurant has no real consequences. Everything is firmly contained in the possibility that all this is just a liberating fantasy. The dog transformation is somehow always Dr Jekyll, and her “nightbitch” persona frankly never becomes a very interesting metaphor for depression or midlife crisis. Yet there’s no doubting the sympathy and vehemence of Adams’s performance.

• Nightbitch is in UK and Irish cinemas from 6 December.