Oliver is a young non-verbal autistic boy. He uses a smartphone to communicate with people. He attends school and is mostly taken care of by his mother, Sarah. His father Marty spends most of the time at work trying to make ends meet. Sarah and Marty’s marriage has become difficult to the extent that Marty moves out. Oliver is bullied and teased by his classmates due to his condition. One night Oliver sees an app on his smartphone, “Misunderstood Monsters”, narrating the story of a monster named “Larry”, who “just wants a friend”. Odd things begin happening to Oliver after he reads the story; lights going out by themselves, a second face appearing on his tablet while he plays with a picture app.
One night his mom organizes a sleepover so Oliver can become more social. Oliver hides the tablet as he is terrified of it. One of the boys thinking Oliver is hiding candy, retrieves the tablet, and reads the story. The lights go out and Larry appears, he can only be seen through the camera of the tablet. Larry attacks one of the boys and Sarah goes to see what the commotion is about. The terrified boys blame Oliver for the incident. Sarah soon begins to see the same weird things Oliver sees, like the lights going out and hearing a strange presence in the house. Sarah rushes to school to pick up Oliver and visits her husband who has since moved out. Sarah now believes Oliver, but Marty is reluctant to do so. That same night Marty takes Oliver to his parking lot attendant job overnight.
Unknown to Marty, Oliver has taken the tablet with him and soon Larry begins to stalk them. Marty thinks the lights going out is just a fluke but soon picks up the tablet and sees Larry picking up Oliver from the ground. Marty rushes them home. Now a believer they break the tablet and assume all is good. The boy that was attacked by Larry during the sleepover at Oliver’s house is traumatized from the incident but soon comes clean on what really had happened. One night at his job Marty is attacked by Larry, at this point, it is evident Larry travels through electricity and can use any mobile device to communicate with people. Marty is hurt but alive. Larry then proceeds to attack Oliver as he intends to take the boy to his world. Sarah realizing the threat trashes all electrical devices with a screen in the house-(including the TV). Larry then appears in physical form and can be seen without a tablet. Oliver and Sarah run to an open field where there is no electricity, at least they think, but when Oliver was bullied at the beginning, his phone was taken and tossed in the same field by one of his bullies. Larry appears and takes Oliver with him.
Oliver must take Larry’s hand to enter Larry’s world, but Sarah appears and takes Larry’s hand instead, saying “I’ll be your friend Larry”, making the ultimate sacrifice for her son. In their final moments Oliver looks Sarah in the eyes for the first time, something Sarah was struggling from within ever since Oliver was diagnosed. Larry takes Sarah and they vanish. Oliver stays with his father, and they intend to deal with the loss. Marty gets more involved with Oliver’s therapy.
One night while sleeping the lights begin to go out again and noises are heard downstairs. Sounds of laughter are heard from the living room, and Marty rushes to see what is going on. He grabs his phone and sees Sarah and Oliver playing happily. Sarah tells her son “I’ll protect you” as Marty smiles.