On the Upper East Side, White Mike, once a wealthy, carefree teenager, now struggles to scrape out a living as a pot dealer; he deals to his former classmates. His mother died a year prior, her treatment consuming his family's wealth and leaving Mike emotionally scarred. Mike's good friend, Molly, does not know he is a drug dealer. Mike's supplier, Lionel, also deals with addictive drug cocktail "Twelve" to Mike's cousin, Charlie. Charlie attempts to mug Lionel, since he is unable to pay for the drug. Lionel shoots Charlie and shoots an innocent observer, Nana. Mike and Charlie's good friend, Hunter, is taken into custody for the murders.Several other young residents of this wealthy Manhattan scene are introduced at a party as customers of White Mike, including Tobias, Yvette, Sara, Jessica and the party's host, Chris. Jessica tries Twelve for the first time, leading to an addiction. During the party, Chris' older brother, Claude, a sociopath and weapon collector, returns home after breaking out of rehab. Their mother discovers this and threatens to call the police. Sara manipulates Chris into throwing a huge birthday party for her, just before the end of spring break. She and her friends invite everyone they know in order to make Sara's birthday "famous".Out of drugs and money, Jessica asks Lionel to stop by Sara's party so she can buy more Twelve. Tobias meets Molly during a drug deal with Mike, and invites her to Sara's party. Mike sees this, and calls him to get him away from Molly. Mike meets up with her, where she tells him about Tobias and the party. Molly suggests visiting Mike at his job, which Mike denies before running off. Molly decides to go to the party.As the party starts, Claude locks himself in his room, practicing with his weapons. Lionel arrives, but is furious with Jessica, as she does not have the money she promised. Since she has no money, she first offers him oral sex, then to have sex with him, which Lionel agrees. Mike's father calls him to deliver the news that Charlie is dead, his body identified. Mike tries to call Molly, who does not answer her phone. He goes to the party to locate her, but is stopped by several drunk party-goers. He accidentally stumbles upon Jessica and Lionel having sex.Startled, Lionel begins to draw out a gun, which Mike recognizes as Charlie's. As Mike begins to accuse Lionel of the murder, Lionel shoots him, causing Claude to pull out his weapons and begin shooting up the party. Teenagers rush out of the party, but many others are killed, including Lionel. Claude hears police sirens and runs outside to die in a suicide by cop fashion. As Sara lies dying, her last thought is how this will make her famous. Mike wakes up in the hospital and Molly reprimands him for his drug-dealing livelihood. He wants to call her when he is sent home, but she says no. Mike visits Nana's mother, and together they connect over their shared grief. Mike comes to terms with his mother's death.