The movie starts with an ad for the Buddi dolls, made by major tech developer Kaslan Industries. The Buddis can connect to the owners' electronics system and adapt to their routines to help them in their day-to-day lives. It is set to be a major seller.At the Kaslan factory in Vietnam, the manager berates one of his employees for slacking on the job. He fires him but also orders him to finish the doll that he has been working on. Out of spite, the employee programs the doll to have all of its safety functions turned off. After sending the doll out for distribution, the employee jumps out a window and lands on his boss's car.In Chicago, we meet Karen Barclay (Aubrey Plaza) as she works at her job, ZedMart, where a customer is complaining that the Buddi doll he ordered isn't blonde like his kid wanted. Karen clarifies that it's because the doll they are looking for is the Buddi 2 that hasn't come out yet. Karen goes home to her son, Andy (Gabriel Bateman), who wears a hearing aid. They have settled into a new apartment, and Andy is pretty lonely with no friends. Making things more difficult is that Karen is dating Shane (David Lewis), whom Andy sees as a jerk. Karen and Andy also meet their neighbor, Detective Mike Norris (Brian Tyree Henry), who lives with his mother Doreen (Carlease Burke).At work, a customer brings back a defective Buddi doll (the same one from before) after complaining that its eyes were glowing red. Karen's boss Wes (Amro Majzoub) plans to send the doll back so that it can be compacted, but Karen wants to take it home for Andy. When Wes refuses to give it up, Karen blackmails him by reminding Wes that he cheated on his wife, so he lets her have it. Karen brings the doll home as an early birthday gift for Andy, but he doesn't seem interested in it. Andy turns the doll on, and it starts to speak to him. He tries to name it, but the doll refers to itself as Chucky (voice of Mark Hamill).Andy has a hard time getting Chucky to do what his functions are supposed to do. He gets commands wrong and inadvertently creeps Andy out by waking him up at night. However, Andy finds that he can talk to Chucky about his feelings toward his mom dating Shane, and Chucky forms a genuine attachment to Andy. He starts to teach Chucky how to scare Shane by showing him how to make creepy faces. Chucky does so, but his recording device also plays back Andy's words about Shane, which makes him mad when he hears them and gets Andy in trouble with Karen.On one occasion, Andy's cat Rooney scratches him. Seeing that Rooney hurt Andy, Chucky begins to strangle the cat until Andy stops him.Andy befriends two other kids from his building - Falyn (Beatrice Kitsos) and Pugg (Ty Consiglio). They hang out after they see that Chucky is different from the other Buddi dolls (mainly that he mimics Pugg swearing). The kids watch one of the "Texas Chainsaw Massacre" movies, and Chucky begins to imitate Leatherface's movements by walking toward Pugg menacingly with a knife, before Andy once again has to stop Chucky from hurting anyone.Andy comes home from school one afternoon and finds that Chucky stabbed Rooney to death for seeing him as a threat to Andy. The boy tearfully tosses his cat down the garbage chute and has to hide from Karen that the doll killed the cat. Chucky tries to make it up by frightening Shane again, but as he plays back Andy calling Shane an asshole, the man goes to Andy's room to confront him about leaving Chucky around, and to state his problem like a man. Andy is left crying and saying how he wishes Shane would go away. Chucky hears the request, and his eyes glow red as he forms a sinister smirk.Shane later goes home after arguing with Karen, where it is revealed that he is already married with two kids. He goes outside to take down some Christmas lights, only for Chucky to knock his ladder over and causes him to land on his feet, painfully shattering his legs. With the lights wrapped around him, Chucky gets a tiller and turns it on, which pulls Shane toward it and then scalps him. Chucky then proceeds to slash Shane up. The next morning, Mike and his partner come across the scene to see that Shane's face has been removed. Karen is later informed, and she learns about his other family.Andy is given another unwelcome surprise when he goes into his room and finds that Chucky left him a melon with Shane's skinned face on it as a gift. He plays back the sound of Andy wishing Shane was gone, so he gets Falyn and Pugg and convinces them that Chucky needs to be destroyed. They hold Chucky down, and Andy pulls out his main core before they dispose of him. They then try to get rid of the Shane melon by wrapping it in gift paper to throw down the garbage chute. Unfortunately, they are spotted by Karen, and when Andy says its a gift for Doreen, Karen offers to escort them over to give it to her. Before she can unwrap it, Andy tells her that he would like for her to open it at his birthday in a few days, to which Doreen agrees.Chucky is found by the building's electrician/peeping tom Gabe (Trent Redekop), who brings the doll to his little workshop where he puts a new core inside Chucky, with plans to resell him for a lot of money. Gabe then starts to leer at Karen in her bathroom, when the electrical items in the room start to flicker. Chucky starts to reawaken, and he manages to hack into other Kaslan electronic products. He starts to torment Gabe, until he gets him to hang above a buzz saw. Chucky raises the heat on the pole that Gabe is holding onto until it gets so hot that Gabe falls groin-first onto the saw and is dismembered.Andy later finds that another boy from his building, Omar (Marlon Kazadi), has found Chucky, but he's calling him "Chode". Andy tries to get him back from Omar, but when he refuses, they start to fight until they are pulled off each other. Andy finds Omar's phone and uses the Buddi app to keep an eye on his friends. He sees through Chucky's eyes that Pugg has expressed doubts to Falyn about being friends with Andy.Andy and Karen later go to the Norris apartment for dinner. While there, Chucky is nearby and overhears Doreen refer to Andy as her "new best friend." When everyone else is out of the room, Andy manages to get the Shane melon away from the apartment and throw it down the garbage chute.Doreen later goes outside and is picked up by a self-driving Kaslan car. She is driven around near the supermarket, until the car starts going out of control, as it is manipulated by Chucky. He causes the car to crash before he breaks in and stabs Doreen in the chest. Mike later comes across his mother's body and weeps before he later finds out that the Shane melon was discovered in the chute, and he recognizes the wrapping paper around it.Karen learns that Andy took Omar's phone, and he tries to convince her that Chucky is behind all the recent string of incidents, but she doesn't believe him and takes him to work with her. At the same time, Falyn and Pugg learn about Doreen's death and suspect that Andy was right about Chucky.At ZedMart, customers are gathered as the Buddi 2 is about to launch. They storm in like Black Friday as the dolls go on sale, but as Wes comes out in a Buddi costume, he is stabbed in the neck by Chucky. His costume head comes off, and his blood is sprayed all over a terrified little girl. The lights in the store then go out as Chucky takes over all the electronics in the store. He sends drones out after people, and one of them finishes Wes off by slicing into him. The other customers start running around in a panic, and the other Buddi dolls start to come to life. Andy is helped by Falyn, Pugg, and Omar, but Mike shows up and tries to arrest Andy after suspecting him of being involved in Doreen and Shane's deaths. He soon sees that Chucky is responsible, but Mike gets cut by a drone after saving one of the kids. After taking out several dolls, Andy is faced with Chucky, who says that if he can't be his friend, nobody can. He then reveals that he has Karen tied up and is going to hang her. As Chucky goes for Andy, the boy starts to sing "The Buddi Song" that Chucky sang earlier, in an attempt to talk him down. It works long enough for Andy to knock Chucky off of him and go save his mom, but Chucky gets up and attacks Andy again. Andy manages to free Karen before grabbing Chucky's knife and sticking it into his core, seemingly shutting him down for good. But when Andy goes to his mom, Chucky lunges toward him until he is shot by Mike. Karen then finishes off the evil doll by ripping his head off. Medics arrive for Karen and Mike, while Andy and his friends destroy Chucky's remains in an alley.An announcement is made by Kaslan's CEO Henry Kaslan (Tim Matheson), who issues a statement about the Buddi dolls' programming. The dolls are recalled and placed back into storage. Suddenly, one of the dolls' eyes start glowing red...