A couple (Rob, a film restorer, and Lexi, a green space architect) has sex in bed in the morning. They then head down to the kitchen where the man reads to their toddler daughter Harper and the wife cooks breakfast while they discuss work. They leave the house, now discussing his job as a film restorer. They pass by two trash cans filled with bottles and remark about how jealous they are of the ability to drink excessively.
The couple stops in at a cafe with their daughter and try to figure out what to do for their date night. Lexi remarks to Rob that a girl is checking him out.
They head over to drop off the baby at the babysitter. The wife gets an email that they landed an interview for their daughter at a really good school and bemoans the fact that they are becoming boring people. The husband reassures her that Harper deserves to go to a great school.
After work, Rob plays with his band
At home that night, Rob and Lexi binge watch a show while drinking wine. Gretchen stands outside of their house smoking and peering in, watching them.
We back up to earlier that same day again and see the same time period from Gretchen's perspective.
Gretchen sits in the cafe with Jimmy, distracted as he rants about his difficulty writing and how he has been distracted. He explains that he needs to meet a writing deadline and that he is imposing a punishment-based system on himself in order to meet writing goals. He instructs Gretchen to mail out one of three letters, horrible things he wouldn't want sent, each time he misses a deadline. Gretchen hardly listens, distracted as she's watching Rob and Lexi chatting across the cafe.
Gretchen leaves and follows the couple down the block as they chat about Harper's school interview. She waves at Harper after she's dropped off at the babysitter's house.
Gretchen joins Edgar and Jimmy at the bar where Jimmy is "writing" -- aka, playing darts with Edgar and drinking. Gretchen wonders aloud about whether a single moment can set a life off on a whole new course and whether subsequent decisions can get you back on the track you were "supposed" to be on. Jimmy basically ignores her and rants about how writing actually consists of very little time spent actually writing.
Gretchen stands watching Rob and Lexi through the window of their house later that night. Their dog, Sandwiches, barks incessantly and Gretchen quiets the dog by giving him nachos.
Gretchen wakes up the next morning and checks her phone. She realizes something and hops out of bed in a great mood.
Lexi drops off Harper with the babysitter at a grocery store and leaves, with Harper sobbing. A woman bumps into the babysitter causing the juice to spill all over her. Gretchen suddenly appears and offers to help. The babysitter hands Harper off to Gretchen and runs off to clean herself off. Gretchen walks the toddler around the store, showing her things. She moves to exit the store with the baby.
When the babysitter returns from cleaning herself up, she doesn't find Gretchen and Harper anywhere and quickly panics. Gretchen reemerges with the crying child, the babysitter gives Gretchen an angry/suspicious look and grabs Harper back, leaving hurriedly.
Lexi gets home and finds Rob playing on an old Gameboy from his nostalgia box. Lexi grabs the Gameboy out of his hands to play with it herself as he puts away the groceries and rants about how he did not get the grant necessary to prevent the destruction of the silent films in his archive. Rob says he wants to drink a gallon of wine but Lexi reminds him that they said they wouldn't drink because they have the interview tomorrow. Rob goes outside to feed the dog and finds him missing.
Gretchen, who has stolen the dog, takes the dog all around town, walking him, driving around with him, and taking him to a dog park. She lies and overshares with a passerby, pretending to be Lexi and listing off the things she found out about the couple from following them.
Back at their house, Lexi and Rob argue about Sandwiches' disappearance and get into a fight. Rob wants to postpone the school interview but Lexi does not. Gretchen shows up at their front door with Sandwiches in her arms, returning him to the couple and pretending that the dog escaped and she just happened to find him.
Gretchen asks about a chair and is invited in, quickly agreeing to a glass of wine. Gretchen hangs out with Rob and Lexi. She talks to them, and they tell her about the school Harper is interviewing at, and Lexi assures her that refusing to grow up is just as limiting as "settling down."
Jimmy arrives to walk Gretchen home at her invitation and he also chats with the couple. Lexi offers to show him the treehouse that Rob built for Harper and they leave, leaving Rob and Gretchen alone.
Gretchen tries to tell Rob that he and Lexi are great. Rob is unconvinced, immediately beginning to complain about their lives, about Lexi, and about how nostalgic he is for the freedom of bachelor life. He tells her that he's totally down to get a drink with her and Jimmy, and mentions that if he got a divorce from Lexi he'd only be forty four. As he speaks, Gretchen becomes visibly more and more disturbed and upset.
Lexi and Jimmy re-enter and Rob tries to get them all in on continuing drinking by busting out the scotch, though Lexi tries in vain to stop him by reminding him about the interview tomorrow. Gretchen brusquely says that she and Jimmy need to leave and they exit.
As Jimmy mocks the couple as they're walking home and tells Gretchen that he met his writing deadline, Gretchen begins to silently sob without Jimmy noticing.