| Director | Jason Reitman |
|---|---|
| Runtime | 94 min |
| Country | United States |
| Box office | $15.6 million |
Marlo is pregnant with an unplanned third child with her husband Drew. They have a daughter, Sarah, and a son, Jonah, who has an undiagnosed behavioral disorder. Trying to reduce his sensitivity to external stimuli, Marlo brushes his skin nightly. Craig, Marlo's wealthy brother, offers to pay for a night nanny as a baby gift, but she rebuffs him. Marlo has dreams of an underwater mermaid, and also of her son's tantrums.
After giving birth to a girl, Mia, Marlo quickly becomes even more overwhelmed and exhausted than before. After the principal of Jonah's school again recommends that he be placed in a different school because they cannot handle him, Marlo erupts at her and leaves angrily. Afterwards she gets out the phone number for the night nanny.
That night, Tully, the nanny, arrives at Marlo's house and immediately settles in to take control. Despite initial awkwardness, they develop a close friendship over the course of several nights. Tully proves to be an exceptional nanny and also cleans the house and bakes cupcakes for Jonah's class. Tully explains that she is there mostly not for Mia herself, but to help and support Marlo. Marlo begins re-engaging with her family and self, singing, cooking nice family meals, and having fun with her kids. When Marlo mentions that she and Drew have not had sex for some time, and that Drew has a fantasy about diner waitresses, Tully puts on a waitress uniform that Marlo had previously purchased but never used and, with Marlo coaching, has sex with Drew.
One night Tully arrives visibly distressed. She has fought with her "enmeshed" roommate, due to her roommate's anger over her bringing home men. Tully impulsively suggests going into the city for drinks, to which Marlo reluctantly agrees; they drive to Marlo's old neighborhood, Bushwick, Brooklyn. At a bar Tully suddenly tells her she can no longer work for her anymore, explaining that she was there only to "bridge a gap." Marlo yells at Tully for being immature and not understanding how aging is going to steal Tully's youthful body and demeanor. Marlo impulsively steals a bike and rides to her former girlfriend’s apartment, where Marlo herself used to live, but no one answers the door. Tully suggests she may be taking things too far. When Marlo's breast becomes painfully engorged with milk, Tully takes her into a bar bathroom and helps her express the milk. On their way home, Marlo falls asleep at the wheel, ends up in a river trapped underwater in the car, and Tully as a mermaid comes to rescue her.
She is taken to a hospital, where a psychiatrist informs a surprised Drew that Marlo was suffering from extreme sleep deprivation and exhaustion. Drew admits he does not know much about the nanny, and when asked for Marlo's maiden name, he says "Tully".
In flashbacks, events that Marlo and Tully experienced together now show Marlo alone. Tully comes to Marlo's hospital room to say goodbye, and each thanks the other for keeping her alive before Tully leaves. Drew reenters and apologizes to Marlo for not realizing what she was going through and affirms his love of her and their family, which she reciprocates.
At home, Marlo goes to brush Jonah, but he questions whether the procedure is "real", and they decide they no longer need to do it. Jonah says his favorite part of the procedure was always just being with his mother, and they embrace. Marlo goes to the kitchen and puts in earbuds to listen to music while she prepares the kids' lunches for tomorrow. Drew comes in, takes one of the earbuds, and helps to chop food up while they listen to the music together.