The third collaboration between Reitman and screenwriter Diablo Cody appears to be an intensely personal one for the latter: Tully's protagonist Marlo (Charlize Theron), a 40-year-old former free spirit now relegated to housewife duties as she expects her third child, is an obvious stand-in for the stripper-cum-blogger-cum-Oscar winner (for Juno), who now has three young kids of her own.

Unable to cope with the overwhelming demands of a new baby, especially as hubby (Ron Livingston) travels a lot for work and her kindergartner has behavioral issues, Marlo eventually caves in to her rich brother's (Mark Duplass) offer to hire a night nanny, so she can at least get some sleep. Soon, the titular Tully (Mackenzie Davis) shows up one evening, a hipster Mary Poppins, and improves Marlo's life literally overnight.

From the get-go, there's clearly something off about Tully. All positive reinforcement and boundless energy, she simply seems too good to be true. (Davis, whose ambiguously dark nature made her a standout in Blade Runner 2049 and the disappointing Always Shine, is well cast.) Tully thus turns into one of those movies where you're basically waiting for the other shoe to drop.

Cody and Reitman drop hints: we see scattered images of mermaids early on; Tully only appears at night and waits to be invited in, vampire-style; nobody seems to interact with her directly except Marlo and her baby. While Cody meditates on the woes of letting go of your wild child past as you approach middle age, the rest of us spend the time guessing just what her script's reveal is going to be.

I won't give away said reveal here, but it becomes clear at some point that there will be no drastic tonal shifts in the film. So when the twist finally comes, it's appropriate to the theme, but it has a very, very soft landing.

Unless you can personally relate to Marlo's predicament – and in truth, I know several women who could – Tully is not essential viewing. Still, it's nice to see such a personal script land a big star and theatrical distribution. And Theron is great as usual.