Pregnant Hannah wakes up to find Marnie spooning her, surprised to find her there. Marnie offers to help Hannah raise the baby. Hannah reluctantly agrees.
In a five months later flash-forward, Hannah takes her new baby boy Grover to the doctor. She's concerned about his weight loss and the fact that he stopped breastfeeding after six weeks, but the doctor covering her normal doctor is unconcerned. Marnie is in the waiting room, happily playing the role of "Aunt Marnie." She encourages Hannah to keep trying to breastfeed Grover. In the car on the way home, Marnie sings and Hannah repeatedly asks Marnie to stop singing, finally yelling at her about it.
In the house, Hannah repeatedly tries to breastfeed Grover and it keeps not working. Marnie keeps trying to give her tips and show Hannah up when it comes to swaddling, annoying Hannah. Marnie tells Hannah she wants to go to a local wine bar for jazz night, but Hannah shuts her down. That night, Hannah bursts in while Marnie is taking sexy lingerie photos of herself, crying about the fact that Grover is crying and that he hates her.
Loreen shows up to help Hannah, having been called by Marnie. Hannah gets angry at Marnie for calling Loreen, but Marnie says that Hannah hasn't been acting mature and everything going on is "above her paygrade." They get into an argument, where Hannah accuses Marnie of having begged to come help with Grover but now that it's not as she imagined, she's uninterested.
Loreen sits with Hannah as she's in the bath and tells her that she also wasn't able to breastfeed and Hannah turned out fine. She gets upset at her mother and accuses her of not telling her it would be this hard. Loreen points out that this is the first decision that Hannah has made that she can't take back, calling bullshit on Hannah's claim that Grover hates her. Hannah insults her mother, blaming Loreen marrying Tad, a gay man, for Hannah's inability to make a normal home/family life for herself. Hannah storms out and goes for a walk where a man driving by asks if she's okay and she angrily tells him she isn't a hooker.
Marnie has Facetime sex with a guy, pretending to be a British flight attendant and that the guy is a pilot. It's very awkward. Loreen interrupts, barging into the room to ask whether they're out of breast milk. Later, Marnie tells an apologetic Loreen that she wasn't masturbating, she was videochatting with a guy named Dalton P. from Weehawken. Loreen asks if she's happy here with Hannah. Marnie claims that it's not her time to be happy because Hannah and Grover need her, but Loreen suggests it's best for their friendship if Marnie is happy. Marnie comes around about Hannah using formula for baby Grover, saying that the ingredients aren't even that bad.
Meanwhile, Hannah goes for a walk by herself. She comes across a teen girl freaking out and running away, pantless and without shoes, saying she was in an emergency situation. Hannah tries to help the girl, even giving the girl her own pants and shoes. Then she finds out that the girl wasn't in an emergency at all -- she ran away after her mom told her to do her homework. Hannah rails at the girl about her mom loving her and taking care of her, demanding her pants back. The girl calls her psycho and runs away with Hannah's pants.
As she's walking home, a pantless Hannah comes across a police officer who drives up to her. The police officer asks if she's okay and Hannah confirms that she is, declining his ride home. He slowly follows her as she's walking home to make sure she gets back okay.
Back at the house, Marnie and Loreen sit outside, drinking wine and smoking. Marnie talks about what might be next for her. She says she was always interested in going to law school because she loves all the rules. Loreen suggests that she be a judge. Hannah arrives, pantless, confusing the two of them.
Hannah joins them, taking a glass of wine. She asks where Grover is and Marnie tells her that he's asleep in her room, and that they gave him formula and he liked it. When Grover starts crying, Hannah declines her mother and Marnie's help, going up herself to take care of him. The baby finally latches, as Hannah softly sings to him and encourages him.