The Day The Earth Stood Still is an Earth based science fiction which was released in 1951 and is directed by Robert Wise.
Coming so soon after the Second World War, the main threat to Earth as the producers saw it was from Nuclear Weapons. The central point was that Earth instead of building more and more deadly weapons, they should be making moves to peace.
Klaatu arrives in Washington DC with his robot Gort to bring a message of peace. He is shot by a soldier who believes he is a threat. The Government rushes him to hospital whilst his robot companion watches over his spacecraft. Failing to get an audience with the President then failing that, an audience with other world leaders at the United Nations which he is told is not possible. He assumes the identity of Mr Carpenter and leaves the hospital. He ends up at a boarding house where he meets Helen Benson and her son which he gets on well with. When Mrs Benson goes out with her boyfriend, he takes the child round Washington to see the sights such as Arlington Cemetary where the military dead are buried. He visits a professor who was not in at the time. Klaatu completes the equation he had been working on after being advised by the son that he is the greatest person alive currently.