‘Tully’ goes beyond one-liners to make emotional connection

Marlo, the main character in “Tully,” fends off small talk with a barrage of acid-dipped put-downs, and dismisses anything sentimental as corny. So you wonder what she would think of this film, which conceals a tender heart within an outer skin of sandpaper.

That’s not a knock; I like “Tully,” a film that makes hipster sincerity look good. Its approach is the modus operandi of screenwriter Diablo Cody and director Jason Reitman, whose 2007 film “Juno” also took pregnancy as its jumping-off point.

“Juno” coasted along on its cutesy one-liners and a very conventional resolution. Thankfully, “Tully” is thornier and wearier, with an authentic sense of both dejection and hope.

You can see why Marlo’s defense mechanism runs hot. Ignored by a husband who retreats into video games, pregnant with her third child, and struggling mightily to understand a son with special needs, she must also bear the questioning gazes around her. Her second pregnancy brought on postpartum depression. What’s going to happen this time?

Charlize Theron, who previously worked with Cody and Reitman on “Young Adult,” gets every ounce of Marlo’s weariness, and also her quippy attitude. She always looks as though she’s plodding around in an old unbelted bathrobe, even when she’s not.

This is one of those rare times that an actor’s weight gain is truly justified, even more than Theron’s Oscar-winning turn as the beefy killer in “Monster.” This film’s depiction of motherhood is so intensely physical, it makes sense for Marlo to look as though she’s moving around in an unfamiliar wrapper. “What’s wrong with your body?” Marlo’s daughter asks her. She doesn’t answer.

Then things change. Marlo’s financially successful brother (Mark Duplass) and irritatingly chipper wife (Elaine Tan) offer a baby gift: picking up the tab for a “night nanny,” someone who stays overnight for a few weeks and tends to baby so the parents (reliable Ron Livingston plays Marlo’s zoned-out husband) can get a reasonable amount of sleep.

Marlo’s nanny is Tully (the very-nearly-weightless Mackenzie Davis, from “Blade Runner 2049”), a remarkable young woman who waltzes in like some fantastical blend of Mary Poppins and Oprah Winfrey. She doesn’t just look after the new baby, she provides wise counsel and mixes up a mean batch of cupcakes.

Her arrival sparks something dormant in Marlo, and for a while the movie is touched by a Frank Capra-like magic, as though an angel had dropped down to prove that it’s a wonderful life after all. Things don’t work out the way we expect, as the story moves toward an ending that might warrant Marlo’s disapproval but seems to me entirely earned.

There are enough caustic jokes in the film to demonstrate that Cody could write these all day if she wanted to; Marlo has a great moment when she cruises past a beloved former bakery and wistfully sighs, “People ate flour back then.”

This movie doesn’t settle for the one-liners. This time Cody is more invested in building a credible emotional life for Marlo, and Charlize Theron is right there to do the heavy lifting.

“Tully” (3½ stars)

An overwhelmed mom (Charlize Theron) agrees to take on a “night nanny” (Mackenzie Davis) when her third baby arrives — and the nanny brings about a fantastical change in mom’s attitude, at least for a while. This tricky film from “Juno” writer Diablo Cody and director Jason Reitman conceals a tender heart within its sandpaper skin; not everybody will buy its premise, but it earns its ending, propelled by Theron’s strong performance.

Rating: R, for language, subject matter

Showing: Alderwood Mall, Everett Stadium, Marysville, Meridian, Pacific Place, Seattle 10, Woodinville, Cascade Mall