widow Helen Benson and her son Bobby. Klaatu becomes a mentor to Bobby, while Helen's suitor, Tom Stevens, becomes jealous of the stranger. The boy takes Klaatu on a tour of the city, including a visit to his father's grave in Arlington National Cemetery; Klaatu learns that most of the dead are soldiers killed in wars. They also visit the Lincoln Memorial. Klaatu asks Bobby, "Who is the greatest living person?" Bobby suggests Professor Barnhardt. They visit the scientist's home, but he is out; Klaatu is able to enter and sees that Barnhardt's blackboard is covered with equations (attempting to solve the Three Body Problem). Klaatu adds to them and, after being discovered by the housekeeper, leaves his contact information. That evening, a government agent escorts Klaatu to Barnhardt. Klaatu tells Barnhardt that the people of other planets are concerned about Earth's possible aggression, now that humanity has developed rockets and rudimentary atomic power. He states that if his message is ignored, Earth could be "eliminated". Barnhardt agrees to gather scientists from around the world at the saucer; he also suggests that Klaatu peacefully demonstrate the power he represents beforehand. Klaatu returns to his spaceship, unaware that Bobby is following him. Bobby watches as Gort knocks out two soldiers so Klaatu can reenter the saucer. Bobby runs home and tells Helen. She does not believe him, but Tom is suspicious. The next day, for half an hour, starting at 12 noon (east coast time), all electrical equipment on Earth ceases to function, except for essential services, such as hospitals and aircraft in flight. Klaatu learns that Bobby watched him the previous night. He visits Helen at work, reveals his purpose on Earth, and asks that she not betray him. Helen asks Tom to keep Klaatu's identity secret, but, he refuses to listen, already in the process of alerting the military. Helen and Klaatu rush to Barnhardt's home. They hope that Barnhardt can hide Klaatu until the meeting that evening. Klaatu tells Helen that if anything should happen to him, she must go to Gort and say: "Klaatu barada nikto". The Army tracks them in their taxi. Klaatu is shot and killed, and his body is moved to a nearby police station cell. Helen rushes to the saucer and speaks Klaatu's phrase. Hearing the words, Gort retrieves Klaatu's body, and revives him inside the saucer, though Klaatu tells Helen that his