A suburban teenager comes of age under the destructive guidance of his best friend, an aimless college dropout.
Mo Harries is a regular teenager hanging out with 23-year-old burnout Zeke Presanti, who used to date Mo’s sister. When Mo gets invited to a party to bring booze and drugs, he finds that he is getting respect from the other kids, including his crush Sophia.
Zeke’s influence on Mo takes a turn for the worse when Mo’s parents find that he has been smoking weed and gotten a tattoo, while Zeke’s advice on approaching Sophia backfires and makes her hate him. Things get worse when Mo’s classmate Stacey, who invited him to the parties in the first place, tells the cops that he has been getting drugs from Mo. Mo is arrested at school, and his father and sister order Zeke to stay away from Mo.
A month later, Mo is stuck doing community service and has to switch schools. Zeke gets a new job working at a fast-food spot and catches up with Mo, indicating that their friendship may not fully be over.
Monroe “Mo” Harris blames his older friend Zeke Presanti as he is being called out of class by the principal and a police officer.
Mo’s older sister Kate dated Zeke when they were younger and always paid special attention to make Mo feel welcome. Even after Kate broke up with him, Zeke and Mo remained close friends, despite their major age difference. Mo’s parents, Reuben and Sherri, allow Mo to continue hanging out with Zeke despite their concern about what kind of influence Zeke is going to be on their young son. Zeke, now 23, is in a relationship with Holly, while Kate has just moved in with her boyfriend Doug. Zeke and Kate briefly continue to have an affair.
Now 16, Mo struggles with the social aspects of high school, spending most of his time with Zeke and his friends rather than anyone his own age. Zeke helps Mo acquire drinks for a party held by some seniors after being invited by fellow sophomore Stacey and gives Mo some weed to sell to the other kids. At the party, Mo earns credibility among the seniors for having brought alcohol and drugs. Mo sees his classmate Sophia, they strike up a conversation and she gives him her number.
Mo later takes Sophia out on a dinner date before going back to Zeke’s place to hang out. The boys tape forties to their hands in an effort to make Mo look impressive. Before Sophia leaves, she and Mo kiss. Mo goes back inside to brag to Zeke and Nick about it, earning him the nickname Tongue Daddy. Mo comes home accidentally stoned the next night before a family dinner and after his father finds out Mo is grounded and forbidden from hanging out with Zeke.
Mo begins to ignore Sophia, per Zeke’s advice on how to get girls, which makes her mad. After realizing his mistake he tries to explain the reason for ignoring her but she refuses to listen and walks out on him. Mo gets a call from Holly and he goes over to her place. Holly tells him that she and Zeke have broken up because he was cheating and takes Mo’s virginity to get back at Zeke.
Stacey gets into an accident in his car with a few seniors who are smoking and drinking. Not knowing what to do he ditches the car. The next day, a police officer comes to school and tells him he won’t get in trouble if he tells who is supplying him with the drugs they found in the car.
When the cops show up at a party looking for Mo, Zeke manages to get him out, evade the police, and bring Mo back to his place where Mo cries about how he has become a degenerate like Zeke, even though he never wanted to be. He also admits to Zeke that he slept with Holly and Zeke forgives him and the two reconcile. Zeke tells Mo that he should blame everything to do with the drugs on him, but Mo declines the offer, saying Zeke has done enough and he needs to handle this on his own.
The following day, Mo gets expelled from school and is sentenced to community service. Reuben drives to Zeke’s house and orders him to stay away from Mo.
3 months later, Mo attends another high school and only uses his car for completing his community service. Mo stops at a fast-food restaurant one day and is surprised to see Zeke working at the drive-thru window. Mo sits with Zeke and he asks Mo if he wants to hang out the next day and Mo says that maybe they can. But as Mo sits in his car, he texts Zeke to cancel. Zeke can be seen behind Mo’s car, obviously devastated by the news.
The film starts in a high school where Monroe “Mo” Harris (Griffin Gluck) is being called out of class by the principal and a police officer. As he is being led away, his voiceover says that this is not his fault. The blame goes to his older friend Zeke Presanti (Pete Davidson).
Zeke used to date Mo’s older sister Kate (Emily Arlook). Mo would hang out with them a lot and took a strong liking to Zeke. After Kate dumped him, Mo still enjoyed hanging around Zeke since he let him do stuff that older kids did. Mo is now 16 and Zeke is a 23-year-old stoner dropout working a part-time job but with no other real aspirations. Mo’s parents Reuben (Jon Cryer) and Sherri (Julia Murney) allow Mo to hang out with Zeke but are still worried about what kind of influence he has on their son.
Mo joins Zeke with his other friends Nick (Coulson Baker) and Chad (Nick Ziobro), as well as Zeke’s girlfriend Holly (Sydney Sweeney). Zeke gives Mo a particularly strong drink that makes him faint almost immediately. He spends the next morning at school hungover and puking in the bathroom.
Mo is later approached by another student, Stacey (Thomas Barbusca) over a senior “Pimps and Hoes” party he’s going to and was wondering if Mo can score them booze since he heard Mo puking and figured he has access to it. Although reluctant, Mo agrees and takes Stacey’s money for booze and has Zeke help him acquire it. Additionally, Zeke gives Mo some weed to sell to the other kids.
At the party, Mo earns credibility after providing the partygoers with weed. He tries to joke around with an older student, but he gets angry at Mo and needs to be talked down. Mo then sees another classmate, Sophia (Oona Laurence), who is in attendance dressed as Hermione Granger. She and Mo strike up a conversation, and she gives him her number.
Mo tells Zeke and Holly about Sophia, and they each give him differing advice on how to approach her. Holly suggests he be himself while Zeke suggests he take time to ignore her as well. Meanwhile, Zeke secretly still has sex with Kate, who is already in a relationship with a guy named Doug (Esteban Benito). When Mo and Zeke visit Kate and Doug, Zeke acts childish toward Doug even though he is friendly and hospitable.
Stacey invites Mo to more parties as long as he keeps providing drugs. Zeke helps him score more weed and molly to impress the other kids.
Mo takes Sophia out on a dinner date before going back to Zeke’s place to hang out. Nick tapes bottles to their hands so they can all drink. Before Sophia leaves, she and Mo kiss. He goes back inside to brag to Zeke and Nick about it, earning him the nickname “Tongue Daddy.”
While getting more weed, Zeke’s dealer makes him smoke with the windows up, leaving Mo very high and reeking of weed. This puts him in trouble when he gets home and finds his grandparents visiting. Reuben knows he is stoned and scolds him, but things get worse when he sees that Mo go “Tongue Daddy!” tattooed on his chest. Mo gets grounded and cannot hang out with Zeke.
Stacey goes to Mo to ask for drugs for another party, but he says he cannot. When Sophia tries to say hi to him, Mo pretends to ignore her, which just pisses her off. Mo then agrees to go out to the party anyway. While there, he tries to explain himself to Sophia, but she doesn’t want to hear it. At the same time, Zeke is hanging out alone after Holly breaks up with him. She later calls Mo and asks him to go to her house. They talk for a bit before they start making out and eventually have sex.
Stacey drives home from the party but swerves off the road while distracted. The other kids abandon him and force him to leave the car in a ditch. At school, the same officer from the beginning goes with the principal to confront Stacey since they know it’s his car. The cop tells him he won’t get in trouble if he tells who is supplying him with the drugs they found in the car.
Kate later calls Zeke to go over to her place so she can tell him straight up to stop hanging out with Mo, and that she has no feelings for him whatsoever anymore. As he drives home, he sees cops closing off the street for a nearby party. Mo is at this party, and the cops are looking for him there. He once again tries to apologize to Sophia, but is interrupted when the cops come knocking. He escapes by climbing onto the roof and jumping into the pool. Zeke finds him and helps him escape. He brings Mo back to his place where Mo cries about how he is becoming like Zeke since he feels that his parents and Sophia hate him and that he is just screwing up. He also admits to Zeke that Holly took his virginity, which Zeke is okay with. He does his best to comfort Mo.
The next morning, Mo is found at school and is brought in with his parents. He gets expelled and is sentenced to community service. Reuben drives to Zeke’s house to punch him in the face and order him to stay away from Mo.
A month passes. Mo switches schools and can only use his car for community service. He stops at a fast-food spot and is surprised to see Zeke working at the drive-thru window. Mo goes inside to eat and catch up with Zeke, who is now using his full name, Isaac. He asks Mo if he would like to hang out the next day, and Mo says that maybe they can.