Charlie Thereon in Tully (Kimberly French)

The writer-director team of Juno and Young Adult are back again, this time with a contemplation on the ups and downs of motherhood and the disillusionment of middle age. Though with a strong cast and plenty of laughs, it falls just short of delivering on its promises in the end.

Also in the mix again is Young Adult star Charlize Theron, as Marlo, a mother of two with a third on the way. A few days into her maternity leave, her wealthy brother (Mark Duplass) offers to hire a “night nanny,” which he describes as someone who will watch her baby while Marlo gets some sleep. Marlo, in acerbic Diablo Cody–speak, answers back that getting a night nanny sounds like the premise to a bad Lifetime movie. After the baby is born, we are treated to a Requiem for a Dream–esque montage of the grueling takeover of one’s life that is having a newborn (wipe-diaper-pump-wipe-diaper-pump). Marlo calls for backup.

Enter Tully (Mackenzie Davis), a cut-off shirt-wearing manic pixie dream girl who arrives like a hipster Mary Poppins, rapping her fingers against Marlo’s front door instead of knocking. Tully walks into the house like she already knows her way around, prattles off some obscure literature quote, and then pledges to not only help with the newborn but to treat Marlo’s life as a whole (to which Marlo replies, “No one’s treated my hole in a really long time,” because this is a Diablo Cody movie and its characters talk like that).

There are very few screenwriters whose names are used to promote films. Historically, it’s rare. Beginning with 2007’s Juno, Cody has built a brand around misanthropic female protagonists and sharp dialogue (which goes just a tad too far to sound natural, as noted above). She has made two well-received films with Reitman (Juno and Young Adult) and a decent TV series, The United States of Tara, but her record hasn’t been smooth. Did anyone even see Ricki and the Flash (or remember it)?

Theron dips back into the transformation bag that garnered her a best actress Oscar for 2003’s Monster. Reportedly she gained 50 pounds to play this role. On par with Monster, this is the actress at her least glamorous. Marlo is an exhausted woman, and Theron’s performance is so believable you can’t help but have sympathy pains along with her.

Davis is simply one of the best up-and-coming actresses working today. She turned in four solid seasons on the criminally underseen Halt and Catch Fire and appeared in the memorable Black Mirror episode “San Junipero.” Her performance as Tully is yet again excellent. The character is young, idealistic, free-spirited, but offers just enough hints that something is definitely off about her. Those of us a little older know that once she figures out how the real world actually works, it’s going to hit her like a ton of bricks. Which is basically the theme the film is working out: Can a person ever get back the spark they had when they were young, or is it true that when we reach adulthood, we awaken to reality?

The film starts out very promising. A standout scene is when Marlo and her husband, Drew (Ron Livingston), have dinner with her brother and sister-in-law (Duplass and Elaine Tan), a nouveau-riche couple spouting off progressive, over-the-top bourgie-isms. The setup and introduction of Tully as the spritely young nanny/new best friend adds to a great beginning, but about two-thirds of the way through, the story line begins to wobble. The climax arrives abruptly: everything that has been built up suddenly falls apart. Let’s just say something unexpected happens.

The ending is going to divide viewers on this film. In a meta-narrative twist, the movie actually takes a turn into one of those clichéd melodramas on Lifetime, not the sensational kind of fare alluded to earlier but one of the more somber ones that tackles a real-life issue—that’s as much as I’ll say. But the twist just didn’t feel like it needed to happen.

One has to wonder how many discussions there were between writer, director, and producers over whether this was the right way to go. It felt like Cody painted herself into a corner and relied on a deus ex machina that felt a little too M. Night Shyamalan than we have come to expect from her. But then again, this is the same person responsible for the much-maligned horror/black comedy Jennifer’s Body.