Let's get the nasty part out of the way first: Tully has a fantastically misjudged ending. It's so incredibly bad, in fact, that it gives me hope for cinema. It feels like every last movie gets micro-managed to death, but the last dozen or so minutes of this are so wildly unsatisfying in such immediately obvious ways that you can absolutely tell that screenwriter Diablo Cody and director Jason Reitman fervently, passionately believed in that ending, and no studio note ever came down suggesting that they might want to change things slightly, or if such a note came, it was laughed at and then ignored.

Anyway, the ending will have to remain in the land of spoilers, except that I'll say that I can definitely see where the filmmakers wanted to go with it, but I think they missed by a lot, and in the process did a lot of damage to what had been wonderful about the film up to that point. And I do even kind of mean wonderful: when it's working, this is the best thing in the careers of Cody and/or Reitman, who have collaborated twice in the past, on 2007's Juno and 2011's Young Adult. Juno has remained the best film either of them has been involved with (though Reitman's career has tanked much harder than Cody's), but Tully repeatedly trounces it.

The film is the story of Marlo (Charlize Theron, the star of Young Adult), a 40-year-old mother of two with a third on the way, like, any minute now. She's constantly exhausted even before the birth, she's already been through one nasty case of postpartum depression, and her husband Drew (Ron Livingston) is no help at all, so when her sanctimonious rich asshole brother Craig (Mark Duplass, who looks way more like Livingston's brother than Theron's - distractingly so) offers to hire a "night nanny" for her, it takes only a few miserable nights with a sleepless newborn to convince her, however begrudgingly, to take him up on the offer. Soon, the effervescent 26-year-old Tully (Mackenzie Davis) is on her doorstep, and Marlo is able to recover, get some sleep, and generally get her shit together for the first time in many years. Meanwhile, it becomes more and more clear that Tully is way too close to the young woman Marlo used to be, and it gets Marlo to thinking about how her life might have gone in different directions, and why she's not even necessarily sad that it didn't.

This is easily Theron's movie. Cody has some very nice observations, and the single best line she's ever written, as well as one of the best metaphorical summaries of a happy marriage I can remember seeing in a movie (it's about which animal on a carousel best represents Drew). Reitman mostly stays out of the way, which is pretty much all I can bring myself to hope for (though I am very pissed at him and director of photography Eric Steelberg for all the pointless handheld cinematography littering the movie). But Theron blows it out of the water - I am prepared to call it the best performance of her career. Tully is, from the script on up, all about the complete physical and mental exhaustion of motherhood, both as a biological act and in its 21st Century incarnation as a social performance, and that manifests most fully in Theron's stunning work of physical acting. It's already impressive how well Theron evokes a deep, soul-crushing fatigue: the kind where your mind just kind of "stops" right there as you're awake and moving around and talking. And then she starts layering in a simmering desperation that manifests as a stunned, panicked animal look in her eyes, a tensed-up abdomen from which her head and limbs all hang heavily, and line readings that have a kind of remarkable, strangled edge to them, like the only reason she's speaking and not screaming is because screaming takes too much energy. The shift in energy as Marlo starts to recover under Tully's care is thus all the more tangible: as Theron's posture and expressions start to open up, her throat starts to unclench, and her gaze grows more focused.* All that while also plausibly playing a much more patient, happy woman to her children, husband, and the various other adults she has to interact with along the way.

All of Tully's triumphs are thus tangled up and indistinguishable from Theron's, though the movie does generally work to support her. Reitman assembles some very nice montage-type sequences, including an early rhythmic sequence demonstrating the narrow and maddeningly repetitive world of cooking, driving, infant squawling, and breast pumping that defines Marlo's world right now (it is the best thing Reitman has ever done as a director). Cody's script, if you can overlook the fundamentally weird, misjudged, badly-expressed, and atonal ending, has a lot of wonderful little grace notes of how adults in family situations behave, including some inordinately tiny little gestures so minimalistic that they could only possibly have come from real life (Marlo accidentally dropping a phone on a sleeping baby; Marlo getting food spilled on herself at the table and pulling of her top with barely-expressed resignation; Marlo's half-hearted leap to stop a spilled bag of breast milk from dripping all over). And there are some very wonderful echoes and resonances in the structure, moments in the film repeats itself without actually repeating itself, and letting us see the way that patterns can be annoying but also comforting in Marlo's life. The one place where the script typically falls flat is in its jokes: Cody's writing has always been worst when she's most self-consciously quipping, and that happens sometimes in Tully, especially around Craig and his equally sanctimonious wife Elyse (Elaine Tan) - there's a Pilates joke in there that's humiliatingly bad. There's some warmly sarcastic observational humor throughout, mostly where we're laughing in sympathy with Marlo's exasperation, but I have to wonder if this comedy-drama would have been better without the first half of that hyphenate.

Anyway, it's a beautifully-observed slice of domestic life with a powerhouse of a central performance, and a plot that kind of mucks things up; Tully herself is a thematically-productive character but incorporated in a gimmicky way, and the ending makes a muddle out of some things that were better off being simple, and I really don't know that the film needs to try this hard (and I then recall that trying too hard is basically the major fault of Juno as well). It's a fine film, and honest, and presents a major aspect of human life that almost never gets shown in movies with sympathy and good humor, and I recommend it; just, like, be ready for the bottom to fall out, for no good goddamn reason.

*This is very spoiler-adjacent, but I think, in writing that sentence, I just figured out why the ending doesn't work for me: the narrative implications of the ending don't square with the very tangible experience of Theron's physical acting, which comes in on a visceral rather than intellectual level, and therefore beats any little nonsense the script wants us to believe.