*CUT TO THE CHASE*
NOTE: This spoiler was submitted by Jeremy
The film starts with Lisa (Leslie Mann) taking a video of her young daughter Julie (Anniston Almond) as she starts her first day of school. Julie is nervous until she meets Kayla (Noor Anna Maher) and Sam (Hannah Goergen), and the three of them quickly hit it off. Lisa meets Kayla's father Mitchell (John Cena) and Sam's father Hunter (Ike Barinholtz). Lisa and Mitchell get emotional seeing their kids enter school, and Hunter suggests they go for drinks.
Fast-forward to the present. Lisa and Julie (now played by Kathryn Newton) spend the morning together before Julie goes to school. It's the day of her prom, and Lisa is dreading the fact that soon Julie will be going to college.
Mitchell tries to get intimate with his wife Marcie (Sarayu Blue) when he finds a pair of thongs. He puts them in his mouth to tempt her until Marcie reveals they belong to Kayla (now played by Geraldine Viswanathan), at which point he spits them out. Mitchell is very protective of Kayla, even snooping in her room after he finds a cigarette filter in her pants, and then finding a vibrating item that is soon revealed to be part of an electric toothbrush.
At school, the girls sit together for lunch. Julie tells the other two that she plans to lose her virginity that night to her boyfriend Austin (Graham Phillips) because she thinks it will be special. Kayla decides to get in on it too with her prom date Connor (Miles Robbins), though she cares less about it being a special thing. Sam (now played by Gideon Adlon) is more hesitant and says she and her prom date Chad (Jimmy Bellinger) might not go that far, but Sam appears more interested in a girl named Angelica (Ramona Young).
Julie goes home and finds an acceptance letter from UCLA. She is nervous to tell Lisa since she thinks Julie was planning on going to school there in Chicago only 45 minutes away.
At home, Sam gets ready for a pre-prom party at Julie's house. She talks to her mom Brenda (June Diane Raphael) and her stepdad Frank (Hannibal Buress). He tells Sam about how prom night is special in terms of being with friends and cherishing these memories. When she gets to the party, Sam tells Julie and Kayla that she wants in on the sex pact.
The party starts, and Mitchell talks to Lisa since she hasn't returned his calls to hang out like they used to. Hunter shows up at the party uninvited in a limo that he rented for the girls. Lisa and Mitchell haven't talked to him since he divorced Brenda after he slept with Sam's babysitter, and Sam is none too happy to see him either. Mitchell meets Connor and immediately dislikes him for being near Kayla and for having a man bun.
Before the girls leave for prom, Lisa finds Julie's acceptance letter in her drawer. She tries to talk to Julie before she leaves but is unable to work the letter into the conversation. Mitchell and Hunter join Lisa when they hear noises coming from Julie's laptop. They start reading the text messages from the girls' group chat, which is filled with emojis that the adults know are for sexual terms. Their fears are confirmed when Julie writes "#SexPact2018", leading them to realize the girls are trying to lose their virginities that night. Lisa and Mitchell vow to stop this from happening, but Hunter thinks they are crazy for trying to do this. Still, he ends up joining them.
The parents arrive at the prom to look for the girls. The girls themselves are enjoying the night with their dates, but Sam sees Angelica and strikes up a conversation with her. Angelica says she just broke up with her girlfriend, and she playfully touches Sam's hair, leading her to realize they may have mutual feelings. Sam goes to kiss Chad to see whether or not she truly is straight or gay, and Hunter sees it. Sam clearly didn't enjoy it. Meanwhile, Kayla starts to drink liquor and smoke hash that Connor made. The girls and their dates then leave the prom to head to the afterparty.
The parents go to Austin's house where Lisa was told that the afterparty would be. Instead, the three find Austin's parents, Ron (Gary Cole) and Cathy (Gina Gershon) engaging in prom roleplay sex. Ron catches Mitchell outside but since he knows him and Lisa, he's not upset. He casually explains what he and his wife do and that Austin knows all about their sex life. They also reveal that the afterparty is at a lake house. When Ron and Cathy refuse to give up the address, Mitchell realizes that Marcie may have it.
The three go to Mitchell's house to talk Marcie into giving up the address, but she thinks that it's stupid that they are so worried about the girls losing their virginities when it's like a rite of passage for guys. The three manage to distract Marcie long enough to acquire the address to the lake house. Upon arriving there, a couple of guys refuse to let the parents in until they trick Mitchell into doing a beer-chugging challenge. In this case, they get Mitchell to stick a funnel in his ass and chug the beer from there. In the house, Julie and Austin try to find a private room to get intimate, Sam is getting drunk enough to consider sleeping with Chad, and Kayla tries one of Connor's homemade macarons laced with a ridiculous amount of drugs. The cops arrive, forcing everyone to flee. The girls and their dates return to the limo, and the parents chase after them.
In the limo, Sam gets sick and pukes on Chad, causing the rest of her friends (and the limo driver) to vomit uncontrollably. The parents are following closely behind until Sam sticks her head out of the sunroof and barfs on Lisa's car, causing her to swerve and drive into a ditch, leaving the car tipped over on its front. The girls go get cleaned up when Julie sees how many texts and calls her mom has sent her. She calls Lisa, and they argue over her getting into UCLA and what she's planning to do later, to which Julie snaps that she knows Lisa is afraid of being alone and that Julie is trying to get as far away from her as possible. Lisa becomes upset and then has an argument with Mitchell when she tells him that she avoids hanging out with him because he reminds her of what she's going to lose. Hunter then has a moment when he tells the two that he cheated on Brenda because they had been distant for a while before it happened. They then hatch another plan on how to find the girls.
The three return to Austin's house to find one of his parents' phones to see if he told them where they will be heading next. Mitchell sneaks into the house and sees that Ron and Cathy are engaging in a weird sex game where they are both blindfolded and following each other's scents to find one another. Mitchell is trapped and at risk for getting caught until Hunter enters and forces him to go along with the sex game, ending in Cathy twisting Hunter's balls. They do manage to get a phone and learn that the girls are heading to a hotel.
Everyone from prom is at the hotel tearing it up. Austin tells Kayla how upset Julie is, so she takes his room key and goes upstairs to create a romantic set-up for the two of them. Kayla takes Connor into a room so they can get down to business. However, she ultimately decides that she does want the loss of her virginity to be special, so she instead lets Connor go down on her. Sam and Chad go into a room as well, but Sam stops Chad before he can get started as she realizes it's not what she wants. That doesn't stop him from finishing on her despite there being little activity, but he is okay with it.
Mitchell starts kicking every door down until he finds Kayla and Connor. He throws Connor at a wall, which freaks Kayla out until they sit down to talk about what's been going on, and Mitchell being forced to accept that his daughter is grown up and capable of making mature decisions on her own.
Lisa sneaks into Julie and Austin's room and sees the romantic set-up from Kayla. She hides under a bed when the two enter the room. Lisa then has to hide behind a TV when she is in danger of being caught, which causes her to get a small electrocution. She sees Julie and Austin dancing together, and she realizes how happy her daughter is. Lisa sneaks out undetected and lets Julie do what she wants.
Hunter tracks Sam down and talks to her. Although she is initially unhappy to see him, Hunter comes forward over how he's been a bad parent over the last few years, but that he really does love Sam. She then officially comes out to him, and he is ecstatic that she told him first and not Brenda.
The girls reunite downstairs in the lobby. Julie tells her friends that she did it, and while it was painful, quick, and awkward, it was perfect for her. They start dancing, when Sam sees Angelica. She comes out to her friends, who both tell her they love her. They leave her when Angelica approaches them, and Sam confirms their mutual feelings, leading Angelica to kiss her.
Lisa, Mitchell, and Hunter sit at the bar together after the night they had. Hunter prepares to leave, but the other two invite him to stay and have drinks with them.
Three months later, the parents are getting ready to say their farewells to their daughters as they embark on a road trip before heading to college. Lisa tries to hide her emotions but her face becomes Niagara Falls. Julie tells her mom she loves her. Hunter and Mitchell say bye to their daughters as well. After the girls leave, Lisa looks at her phone and sees that she was accidentally added to the girls group chat. They start putting emojis to indicate that they are going to do a lot of drugs on their trip. The three parents start to hop in the car to stop them until the girls say they were just joking.
During the credits, Mitchell and Marcie try out the blindfolded sex game and start to enjoy it until Kayla walks in on them and freaks out.
Three parents - Lisa, Mitchell, and Hunter - learn that their daughters - Julie, Kayla, and Sam - are planning to lose their virginities at prom night, and so the parents set out to talk some sense into their kids.
Over the course of the night, the parents come to terms with their issues involving their daughters. Lisa must accept that Julie wants to go to an out-of-state college and is mature enough to make her own choices. Mitchell must face the fact that Kayla is grown up and that he can't always be around to protect her, but that she can take care of herself. Hunter owns up to being an absent parent after he cheated on Sam's mom years earlier.
Only Julie actually loses her virginity. Kayla lets her boyfriend go down on her, while Sam comes out as a lesbian to her dad and friends before going to hook up with a girl named Angelica.
The three parents rekindle their friendship and see their girls off as they head to college at the end of the summer.