All of Washington, D.C., is thrown into a panic when an extraterrestrial spacecraft lands near the White House. Out steps Klaatu (Michael Rennie, in a role intended for Claude Rains), a handsome and soft-spoken interplanetary traveler, whose "bodyguard" is Gort (Lock Martin), a huge robot who spews forth laser-like death rays when danger threatens. After being wounded by an overzealous soldier, Klaatu announces that he has a message of the gravest importance for all humankind, which he will deliver only when all the leaders of all nations will agree to meet with him. World politics being what they are in 1951, Klaatu's demands are turned down and he is ordered to remain in the hospital, where his wounds are being tended. Klaatu escapes, taking refuge in a boarding house, where he poses as one "Mr. Carpenter" (one of the film's many parallels between Klaatu and Christ). There the benign alien gains the confidence of a lovely widow (Patricia Neal) and her son, Bobby (Billy Gray), neither of whom tumble to his other-worldly origins, and seeks out the gentleman whom Bobby regards as "the smartest man in the world" -- an Einstein-like scientist, Dr. Barnhardt (Sam Jaffe). The next day, at precisely 12 o'clock, Klaatu arranges for the world to "stand still" -- he shuts down all electrical power in the world, with the exception of essentials like hospitals and planes in flight. Directed by Robert Wise, who edited Citizen Kane (1941) and The Magnificent Ambersons (1942) for director Orson Welles before going on to direct such major 1960s musicals as West Side Story (1961) and The Sound of Music (1965), The Day the Earth Stood Still was based on the story Farewell to the Master by Harry Bates.
~ Hal Erickson, All Movie Guide