Plot summary

Qohen Leth (Christoph Waltz), an eccentric programmer who refers to himself in plurals, is assigned to "crunch entities" for a company named Mancom. Finding himself suffering existential angst, Qohen constantly waits for a phone call, hoping that it might bring him happiness or the answers he seeks. Requesting a psych evaluation, three company doctors determine that Qohen is physically healthy, but request he have therapy from Dr Shrink-Rom (Tilda Swinton), an AI therapist designed to provide mental evaluation. Wanting to meet with "Management" (Matt Damon), Qohen attends a party held by his supervisor, Joby (David Thewlis). Stumbling into an empty room, Qohen finds Management and requests to work from home, as he would be more productive and would no longer risk missing his call; Management simply notes he finds Qohen "quite insane."Attempting to leave the party, Qohen is pressed into staying by Joby and, when Qohen starts choking on an olive, he is rescued by partygoer Bainsley (Mélanie Thierry). His request granted by Management, Qohen is informed he is to start working from home, and is shown a massive supercomputer dubbed "The Neural Net Mancive"; containing all of the entities crunched by workers, Qohen is required to order its data to solve the "Zero Theorem", a mysterious mathematical formula. Spending months as a hermit whilst working on the program, Dr. Shrink-Rom diagnoses him with numerous conditions, and he begins suffering nightmares involving a black hole.Frustrated with his work, Qohen smashes his computer with a hammer, and is soon visited by Bainsley. Qohen confides with Bainsley that he believes he accidentally hung up a call that would have given him the meaning of life, and has desperately been waiting for a call-back ever since. Qohen is then visited by Bob (Lucas Hedges), the teenage son of Management. Bob repairs his computer, reveals Management is spying on him, and suggests that Bainsley is only interested in Qohen because she is paid to be. After Qohen insists he will cease working on the zero theorem, Bob promises to get him his call if he continues. Having received an AI suit from Bainsley, Qohen interacts with her through virtual reality; appearing on a beach together, they soon kiss one another.Visited again by Bob, Qohen, to his distaste, learns the zero theorem aims to prove life is meaningless through the Big Crunch theory. Digitally connecting to Bainsley again, Qohen is comforted by her, but when he denounces Management and suggests eloping together, she forcefully disconnects, damaging Qohen's suit. When Bob then takes his suit to repair it, Qohen connects to Bainsley unannounced, only to discover she is a webcam stripper. Bob returns with Qohen's suit, now repaired, and reveals his phone call is only a delusion, and admits his Dr. Shrink-Rom was only designed to identify his pathology rather than treat it. Qohen is visited by Bainsley, who apologizes for deceiving him, but claims she is truly fell in love with him; despite Bainsley's offer to elope, which is encouraged by Bob, Qohen turns her down.Qohen, discussing his problems with Bob, discovers Bob's health is radically declining. Caring for Bob, Qohen finds a hidden camera in his bathroom mirror, and begins to uncover and smash Management's cameras. Despite barricading his home, Management employees break in and take Bob. Visited by Joby, Qohen is berated as his actions got him fired. Wearing his now repaired suit, Qohen connects to his computer, but is electrocuted. Appearing at the Neural Net Mancive, Qohen is greeted by Management, who notes that Bob is hospitalized, and that he suffers from a chronic illness. Management explains Qohen is part of the Neural Net now and, when Qohen asks questions about the meaning of his life, Management shrugs them off. Management explains he chose Qohen as he had faith in a phone call giving his life meaning, effectively making him the antithesis of the zero theorem. Management then disappears, apologizing as he no longer needs Qohen; angered, Qohen smashes the Neural Net, collapsing it and revealing a black hole inside. Smiling, Qohen drops into it, only to appear back on the virtual beach. Qohen stands in the sea and watches the sun set.