This spoiler was submitted by Alex
Journalist David Sheff (Steve Carell) is in the office of addiction expert Dr. Brown (Timothy Hutton). He explains that he’s not there for an article he’s there because he doesn’t know his son anymore he’s a drug addict, doing multiple drugs but most recently crystal meth, and he needs help.
Flashback to one year earlier. David and his wife Karen (Maura Tierney) live in San Francisco with their two young kids Jasper and Daisy and David’s son from his first marriage, Nic (Timothee Chalamet). One night, Nic doesn’t come home. David calls his ex-wife, Nic’s mother Vicki (Amy Ryan). The two get into a heated argument about Nic and his behavior. Two days later, Nic returns home, hungover. With his behavior getting alarming, David goes to see a drug rehab counselor, who says their program has an eighty percent success rate. David enters Nic into the program, and the two hug and exchange the word “everything” to each other.
After some time in rehab, Nic tells David and Karen that he wants to stay on at the rehab center’s extension program, a halfway house, and not go to college right away. Later, David gets a call that Nic has not returned to the halfway home. He angrily wants to know why no one is looking for Nic, but is told that their job at that point is not to locate him, but they will be there if he should return. They say relapse is part of recovery. David takes it upon himself to find Nic, eventually locating him in an alley in the rain. Nic vomits inside David’s car, and David enters him back into rehab. When he and Karen bring him back, he demands to know the full extent of Nic’s drug habits, learning just how many drugs his son is using.
Later on, Nic is doing better and tells his dad he wants to go to college. David is excited and drops Nic off at school. Again, they exchange “everything”s. It goes well at first, and Nic even starts dating a classmate. While at Thanksgiving at his girlfriend’s, Nic finds pills in their bathroom and takes them. He begins doing hard drugs again at school, his relationship falling apart. When he next comes back home, he asks if he can borrow David’s car in order to go to a narcotics anonymous meeting. Instead, he goes out and scores. The next morning, when the two young children get into a fight because Jasper thinks Daisy stole the money out of his piggy bank, David confronts Nic asking if he stole the money. Nic gets aggressive and denies it, but David realizes he’s using again. David says he shouldn’t have let Nic go to school, he wasn’t ready but Nic refuses any more treatment and runs away.
Caught up to the beginning of the film, Dr. Brown explains that crystal meth is extremely addictive, and that no matter what number he was told, the likelihood of someone overcoming an addiction is closer to eight percent. While searching for Nic, David goes through intense experiences buying and using cocaine to try to understand his son’s experience, and meeting and buying a meal for a young addict girl for some insight. Finally, he hears from Nic, but when they meet, Nic is erratic and high, and says he’s clean but needs a few hundred dollars. David refuses to give him money and tries to get him to come home with him, but Nic flees, completely irrational and unreasonable.
Later, David receives a call from a hospital in New York telling him Nic has overdosed. David flies to New York only to find Nic checked himself out against doctor’s orders, but as he is on his way to fly back to San Francisco, he hears from Nic. He meets him at a diner, and Nic tells him he wants to get clean. In a flashback to when David first sent Nic to stay with his mother for the summer, we learn where “everything” came from when Nic was sad to leave, his father assured him he loved him more than everything in the world, and they repeated it back to each other.
David speaks with Vicki, and they decide Nic will go to Los Angeles to live with her and continue treatment there. Nic is very successful he graduates college, has a good relationship with his sponsor, Spencer (Andre Royo), and is fourteen months sober. Around this time, he drives down to San Francisco for a visit with David and Karen. He gets along well with his younger siblings, but when he returns late from an NA meeting, David makes him pee in a cup for drug testing. Nic understands why, even though he promises he’s clean. After he leaves his dad’s house, Nic grows anxious and uneasy. He calls Spencer telling him he’s having a hard time. Spencer insists he come over for dinner that night, but instead, Nic goes downtown and runs into his old friend from rehab Lauren (Kaitlyn Dever). The two score hard drugs together, take them, and have sex.
Vicki calls David and tells her that Nic is missing. The two begin blaming each other and have a screaming match on the phone. David once again packs a bag to look for Nic, but Karen tells him she needs him to stay home. When David says he needs to make Nic better, Karen shouts at him that he can’t - he can’t fix this. Later, while his family is out, Nic and Lauren break into their house. When the family returns home, they flee out the back, but Nic’s brother spots them. David and Karen go in different directions, and when Nic takes off in his car, Karen gets into her car and chases after them for miles. She eventually loses them and breaks down crying.
When Lauren overdoses, Nic calls an ambulance, and though the EMTs are able to save her, he is left alone. He calls David, and tearfully begs to come home, he doesn’t want to go to rehab but is willing to come home. David stays firm and tells him he can’t do that; he can’t take care of him; Nic needs to call his sponsor and take care of himself. He wishes his son luck and lets him go. Time passes, and Nic is still missing. Vicki calls and begs David for help finding Nic, but David can’t do anything anymore. Vicki is sure he will be dead soon if they don’t do anything, but David has to distance himself.
David and Karen begin attending al-anon meetings to deal with their situation. Nic overdoses again, nearly dying. David comes to the hospital to see him. He takes Nic, who is very weak, on a walk outside, and the two sit on a bench together. Nic collapses in his father’s arms, hugging him tightly. David rubs his back as the two look to an uncertain future.
The post-script tells us that though it is a constant struggle, Nic has been sober for eight years.