Mae Holland is a recent college graduate and is already unfulfilled in her internship at a call center. Through her friend Annie, she manages to get hired to work in customer services at tech and social media company The Circle Corporation. Annie is thrilled, Mae's friend Mercer, less so. Mae has no choice other than to take the job, because she has already become the major breadwinner for her family; her father suffers from multiple sclerosis, and her mother cannot work because she is taking care of him.
The founder and company CEO, Eamon Bailey, presides over a company meeting one day, deciding to introduce SeaChange, which uses small cameras to film real-time video from anywhere at all. Mae hangs on his every word; she is rising quickly and proves herself to be a master networker. She also comes to the attention of Ty Lafitte, another more senior employee who takes it upon himself to introduce her to the corporation's more influential people. One of these is Chief Operating Officer, Tom Stenton, who is working with a political candidate willing to be filmed throughout her campaigning as part of SeaChange.
Lafitte takes Mae to the engine room of the company - the area that contains the cloud server for all of the information collected by SeaChange. Lafitte is already suspicious of the new technologies; several products that he created have grown and morphed into products that he did not intend them to be at the outset.
After a fight with her friend Mercer, Mae takes a night paddle in her kayak to blow off steam. The waters are rougher than usual and she capsizes, but because there was a SeaChange camera on her kayak, she is recorded; the Coast Guard are able to see her, and she is rescued. Her experience is shared with the company as a whole when Eamon introduces her at the next meeting. Changed by her brush with death, and feeling saved by the power of SeaChange, Mae decides to be the first user to go completely transparent; this involves being filmed by the little camera twenty four hours a day, seven days a week. However, by default, Mae's friends and family are forced to go transparent too. This understandably deeply harms her relationships with her parents and with Annie; they find themselves distancing from her because she has sacrificed their privacy too much. Annie is finding that the new Mae is someone she neither recognizes or likes very much.
At the next company meeting Mae proposes that every individual is required to have a Circle account, and to exercise their right to vote through it. Eamon and Tom predictably love the idea but Annie is concerned. Mae brags that The Circle now have the technology to locate anyone on the planet anywhere in twenty minutes or less. She introduces a program to find felons who are wanted just as quickly. She finds the first wanted felon in an impressive ten minutes. She is then challenged to use the program to locate Mercer, who has not been seen since their argument. They find him at his cabin, which is deliberately isolated from people. He is frightened and flees the cabin, leading his pursuers on a car chase before losing control of the vehicle and crashing off a bridge. He is killed instantly. Annie leaves The Circle after the incident and does not seem keen to maintain contact with Mae.
Mae is almost addicted to her job at The Circle. Even the pleas from her parents to leave the corporation fall on deaf ears. She learns from Lafitte that he has accessed the email accounts of both Eamon Bailey and Tom Stanton, so at the next company meeting Mae invites them both to go transparent, telling them that Lafitte has their accounts anyway and can lay them bare to the world whenever he chooses. Nobody should be above transparency. By this time, Mae is oblivious to the fact that she is watched wherever she goes. After the meeting, she feels better than she has since Mercer's death, and she takes her kayak out onto the water again, seemingly unaware of the drones that circle above her.
