In Southern California, KXLA television reporter, Kimberly Wells, arrives at Ventana Nuclear Power Plant with cameraman Richard Adams and soundman Hector Salas to film a segment for an energy special. During their visit, an unexpected tremor is felt inside the plant. From the soundproof visitors’ gallery overlooking the control room, they observe the operators responding to a malfunction. Although the public relations officer, Bill Gibson, informs them that the incident is merely a “routine turbine trip,” the behavior in the control room indicates a more serious crisis. Richard surreptitiously films the event, even though photography is forbidden. Meanwhile, in the control room below, shift supervisor and nuclear engineer, Jack Godell, calmly directs the operators to stabilize the reactor, but pauses when he feels a milder, secondary shudder, which no one else notices. During the procedure, a stuck indicator causes a misreading of the water level, which is dangerously low and threatens to expose the nuclear core. When Jack realizes the equipment error, he executes a risky maneuver to adjust the water level, then waits with apprehension. As the water begins to rise, he breathes a sigh of relief. Later, plant superintendent Herman DeYoung reports to utility company chairman, Evan McCormack, that there was no damage, but the Nuclear Regulatory Commission (NRC) will be conducting an investigation. With news that the company is losing half a million dollars per day, McCormack urges DeYoung to finalize the investigation at Ventana as soon as possible, so the plant can resume operation. At the KXLA news studio in Los Angeles, California, station director, Don Jacovich, decides that the footage of the control room cannot be broadcast because it represents unauthorized photography of a security installation. Richard is furious, believing that the public should be informed. After noticing Gibson at the station earlier, Kimberly suspects that the utility company may be pressuring Jacovich to suppress the story. The next day, news producer Mac Churchill informs Kimberly that Richard stole the Ventana footage from the film vault and warns her to retrieve it before Jacovich finds out. Looking for Richard, Kimberly stops by a local hangout near the Ventana plant. At the bar, Jack celebrates with his friend and colleague, Ted Spindler, after learning that the investigation is complete and the plant has been cleared to resume operation. Recognizing Kimberly from television, he invites her to join them. When Kimberly reminds Jack that she was in the visitors’ gallery on the day of accident, Jack corrects her and says the malfunction was not serious enough to be called an “accident.” She asks if the public was in danger, and Jack explains that nuclear plants have multiple backup systems, known as “defense-in-depth.” As a result, there was never a threat of radiation exposure. Later at the plant, however, Jack discovers radioactive leakage near one of the pumps. When he examines X-Rays of the pump’s welding seals, he is shocked to discover that the inspectors duplicated X-Rays, instead of examining each welded joint individually. DeYoung refuses to authorize new radiographs, which could cost $20 million, and reminds Jack that the plant must be back online that afternoon. Reluctantly, Jack follows orders, but becomes increasingly concerned about the safety of the plant. When he confronts D. B. Royce, the inspector responsible for the X-Rays, Jack threatens to expose the negligence to the NRC. Meanwhile, Richard takes the Ventana accident footage to a NRC safety hearing being conducted for a new nuclear plant at Point Conception, also owned by McCormack’s company. In a locked room, Kimberly arrives while Richard is showing the footage to physics professor, Dr. Lowell, and nuclear engineer, Greg Minor. Based on the visual evidence, the two experts believe the reactor was close to exposure, which could have caused an uncontrollable nuclear meltdown, known as “The China Syndrome.” In such a case, radioactive clouds would have been released into the atmosphere, leaving a large portion of the state uninhabitable, followed by outbreaks of cancerous diseases. That evening, Kimberly and Richard visit Jack at home and learn that the problem during the accident was not a near-exposure of the core since the reactor’s defense system responded correctly, but rather the falsification of the X-Rays. The unusual shudder Jack felt following the main shock of the turbine trip indicated a weak pump, which could trigger a China Syndrome if too much pressure is applied. Although he has devoted his life to the plant, Jack believes it is unsafe and agrees to hand over the false X-Rays for Richard and Kimberly to present at the NRC hearing. The next day, Hector discreetly collects the evidence from Jack, but he is seriously injured when his car is deliberately pushed off the road by a truck. Unable to reach Hector, Kimberly telephones Jack and asks him to testify in person. Jack leaves immediately, but soon discovers that he is being followed. To dodge his pursuers, Jack drives to Ventana, which has a guarded entrance. Inside the plant, Jack panics when he realizes that the reactor is almost at full power again, and warns Ted that another outage could destroy the weak pump. Ted believes Jack is intoxicated and tells him to go home, but Jack grabs a gun from a security guard and orders the operators to leave the control room. He summons Kimberly to the plant and allows her alone into the control room, announcing that he wants to make a statement on live television. Watching anxiously from the visitors’ gallery, McCormack objects, but DeYoung reminds him that Jack can flood the containment with radiation as long as he has the control room hijacked. While Richard makes arrangements for the broadcast on KXLA, McCormack and DeYoung instruct Ted to trigger a reactor “scram,” or shutdown, from outside the control room, which should distract Jack until a SWAT team can break in and restrain him. Richard informs Kimberly that the camera crew is ready, and she introduces Jack on live television. Jack begins by admitting a serious accident happened at the plant, but has difficulty relating the complexity of the problem and appears flustered. Suddenly, an alarm sounds and Jack screams, knowing that a reactor scram will jeopardize the pump. After DeYoung orders the television cables disconnected, the SWAT team forces open the control room doors and shoots Jack. Before he dies, Jack whispers to Kimberly that he can feel the shudder. Meanwhile, Ted watches a monitor to see the pump responsible for the radioactive leakage coming apart and realizes that his friend was right. The shudder grows stronger and the lights go out, until the reactor stabilizes automatically. Afterward, Gibson informs a crowd of reporters outside that the situation involved an emotionally disturbed, intoxicated employee, but the plant is now secure. At the camera truck, Mac tells Kimberly that Jack appeared unstable during his statement on air, but Kimberly is determined to prevent the posthumous systematic assassination of Jack’s character. On live television, she asks Ted if Jack was disturbed, and he declares that his friend was not a lunatic, but a hero.