The Day the Earth Stood Still ending explained (spoilers)

[Lukarquemaib]

The alien leaves, teaching Earth that war is not the answer, and that Earth will be destroyed if they ever bring war into space and become a threat to other planets.

[Mai Lan]

Klaatu arrived in Washington and was immediately shot, but survived. He asked for a meeting with all of the world leaders but was told this wasnt possible, they would never agree. He escaped from custodyand went into hiding. While pretending to be human he befriended Helen Benson and her son, who later discovered his true identity. Klaatu found Professor Barnhardt, supposed to be the smartest man in the world, who suggested a meeting with the worlds top scientists. He alsorecommended a display of Klaatus power before the meeting to force everyone to take him seriously. Klaatu then turned off the worlds electricity for 30 minutes. En route to the spaceship where the scientists were gathering for the meeting, the military tracked Klaatu down and shot him dead. Helen Benson gave his robot a message from Klaatu and the robot found Klaatus body, returned him to the ship, and temporarily resurrected him. Klaatu delivered his message to the scientists and present military staff, then he and the robot re-entered the spaceship and flew away.