Through her friend Annie (Karen Gillan), call center intern Mae Holland (Emma Watson) secures a customer support position at The Circle, a tech and social media company. Mae takes the job, hoping to support her parents, particularly her father who suffers from multiple sclerosis, while Mae's long time friend Mercer (Ellar Coltrane) is less supportive. At a company meeting, CEO Eamon Bailey (Tom Hanks) introduces SeeChange, which uses small cameras placed anywhere to provide real-time high-quality video. Mae rises quickly in The Circle, embracing social networking and meeting Ty Lafitte (John Boyega), who displays suspicion of other, more enthusiastic employees. At an outdoor company rally emphasizing the need for accountability in politics, The Circle's Chief Operating Officer, Tom Stenton (Patton Oswalt), introduces Congresswoman Olivia Santos (Judy Reyes), who has agreed to open her daily workings to the public through SeeChange. Ty subsequently shows Mae the area containing the cloud server where all information collected by SeeChange is to be stored. Mae is embarrassed when she realizes that Ty is the creator of TrueYou, the Circle's social network, and she had not recognized him. He tells her that TrueYou has grown out of his control, and its current utilization is not what he intended.
Later, Mae's mother shows Mae a picture of a chandelier Mercer made from deer antlers. She photographs it and shares it on her Circle profile. The image attracts significant negative attention to Mercer, with people accusing him of killing the deer. Mercer confronts her at work and tells her to leave him alone. Distressed by Mercer’s reaction, Mae goes kayaking at night and the rough waters cause her kayak to capsize, requiring rescue by the Coast Guard, who were alerted to the emergency through SeeChange cameras, which recorded her acquiring the kayak and capsizing it. At the next meeting, Eamon introduces Mae to the crowd and they discuss her experience of the rescue, which moves her to become the first "Circler" to go "completely transparent," which involves wearing a small camera and exposing her life to the world 24 hours a day. However, this damages her relationships with her parents and Annie, as she accidentally exposes private aspects of their lives to the camera, and they distance themselves from her as a result.
At a board meeting, Eamon announces support from almost all 50 states for voting through Circle accounts. Mae takes it a step further, and suggests requiring every voting citizen to have a Circle account in order to do so. Eamon and Tom approve, but the suggestion upsets Annie. At the next company-wide meeting, Mae says that The Circle believes it can find anyone on the planet in under 20 minutes and introduces a program to find wanted felons in the same time frame. The program identifies an escaped child murderer within 10 minutes, which prompts the Circlers in the audience to erupt in applause. Mae uses this successful test to suggest transparency can be a force for good. Mae says that the program can find anyone, not just wanted felons, and someone suggests Mercer. Mae is initially hesitant to use the program to locate Mercer, but Eamon persuades Mae to continue. Mercer is quickly located in an isolated cabin. Startled by Circle users descending upon his home, he flees in a car, though a Circle user places a small camera on his car window without his knowledge or consent. They pursue him via automobile and a flying drone, which causes Mercer to swerve uncontrollably off a bridge to his death, much to Mae's horror. Days later, Mae calls Annie, who has left The Circle and returned to Scotland, which has improved her well-being. Mae, however, finds that connection with others helps her cope with Mercer's death.
Mae returns to The Circle, despite her parents' pleas. Mae calls Ty to ask for a favor and Ty tells her something that he has discovered. At the next company-wide meeting, Mae explains how connection has helped her recover. She speaks with Eamon, and invites Tom onstage, then invites Eamon and Tom to go fully transparent. She explains that Ty has found all their email accounts and exposed them to the world, as no one should be exempt. Eamon and Tom, clearly upset, try to save face before Tom leaves the stage. Her superiors cut power to her presentation, and the stage goes dark, but the audience activates their mobile devices, illuminating Mae, who reiterates her advocacy of transparency. She later returns to kayaking, untroubled by the drones that shadow her.
