It’s rather impressive how quickly a star can fall in Hollywood. Once upon a time, Jason Reitman was one of the industry’s outstanding young voices, receiving plaudits and Oscar nominations for films like Juno and Up in the Air, as well as critical buzz for Thank You for Smoking and Young Adult. But after his two most recent films, Labor Day and Men, Women and Children failed to move the needle in any appreciable way, it became easy to think that Reitman had lost his mojo. It’s been four years since Men, Women and Children, which seems like an eternity for a guy who made five films in nine years. But now Reitman is back with some familiar faces to make Tully an opportunity to regain some of the magic that made him who he was in the late 2000s.

Tully sees Reitman reunite with screenwriter Diablo Cody, who won the Academy Award for Best Original Screenplay for Juno and was nominated for a WGA award for Young Adult. Also returning from Young Adult is star Charlize Theron, who plays the embattled mother at the center of Tully, Marlo, a mother of two with a third on the way who’s been pushed to the brink by a challenging son (Asher Miles Fallica) and a generally supportive but not particularly active husband (Ron Livingston). Her brother (Mark Duplass) can see she needs help, and offers to hire her a night nanny who will take care of the newborn after hours and allow her to get some sleep and a semblance of calm in an increasingly frenzied life. She is hesitant at first, but relents after things go south with her son’s school. The night nanny, Tully (Mackenzie Davis), soon arrives, immediately taking a shine to both Marlo and the infant, and the change in Marlo’s mood and energy is palpable.

There’s much more than meets the eye to Tully, but we can’t discuss such things without ruining the fun. Rest assured that Reitman and Cody have more on their minds than simply telling the story of an overstressed and overworked mother looking for help, but that aspect of the film is a big part of why it’s so successful. Both Theron and Cody have clearly drawn much from their own experience as mothers, the habitualization and redundancy that becomes the life of a full-time caregiver mixed with the pressures of dealing with a differently abled child prone to fits when confronted with even the slightest change to the status quo. Indeed, much of the beginning of the film plays out as something akin to a horror movie about unexpected pregnancy, sure to scare some members of the audience away from ever reproducing. It’s yet another case of Theron showing her range, similar in some ways to the caustic, deeply wounded woman at the center of Young Adult but shaded with an entirely different brush.

Tully herself is in some sense a 21st century hipster Mary Poppins, whisking her way into Marlo’s life like she flew in on an umbrella to save the day. She’s everything Marlo isn’t: calm and assured and youthful and sex positive and excited about the prospects of life. She’s unmoored from the expectations of polite society and fully focused on the well-being of this beleaguered woman and her new baby, which is exactly what Marlo needs to re-center herself. It’s a match made in heaven, but as we all know, nothing lasts forever. Davis’ profile has been on the rise in recent years on screens both big and small, whether it’s as the lead role in Halt and Catch Fire or in the Emmy winning Black Mirror episode “San Junipero,” or an important supporting turn in Blade Runner 2049. Here, as a sort of Manic Pixie Dream Nanny, she seems impossibly perfect and giving in every way, but that’s backed up by a warmth and wholesomeness and frankness that makes you think she really cares. Tully is an often uncompromising and more than frightening vision of childbirth and parenting in the modern world, but the four creators at its center never lose sight of the decency and empathy at its core.

There’s no question that Tully feels much more apiece with the Reitman of old than the one we’ve seen for the last seven years or so. There’s a comfort to his filmmaking here, similar to that mix of grounded reality and heightened experiences that we saw in his earliest directorial work (at times Juno and Thank You for Smoking feel like they take place in a slightly displaced reality from our own). Diablo Cody has a lot to do with that; the script has a lived-in and experiential feel even as it plays with imagery and dream sequences and hints of magical realism in fascinating ways. And it goes for broke at the end in a way that works more than admirably. The supporting cast does a great job fleshing out the film, and Cody's sense of humor is as sharp as ever. But it’s really the two-hander scenes between Theron and Davis that forms the core of the film, and while mileage may vary about where the film goes in its final act, the journey to get there is bursting with humanity, warts and all.