The Day the Earth Stood Still

Miles Lightyears from the standard sci-fi schlock dished out in 1950s cinemas, The Day the Earth Stood Still is a simply stated parable, a calm warning to a world on the brink of self-destruction.
An immense flying saucer lands in Washington, D.C., deputed by the federated planets to warn barbarous Earth that its violence must be curbed. Klaatu, the spaceman who comes in peace (played by spare, handsome, and unfailingly cordial Michael Rennie), radiates a benevolent gravitas that casts light on the fears and cruelty of the earthlings around him.
When world leaders let their petty protocols delay the meeting, Klaatu (assuming the name Carpenter — get it?) escapes into the city, where the barely contained paranoia and jingoism are relieved only by an Einsteinian scientist, a little boy, and the boy’s widowed mother (Patricia Neal).
The Bernard Hermann score (with theremins!) provides an eerie, spacy atmosphere. Though sometimes stilted and preachy, this thoughtful and eloquent film stands up to the test of time.