No Survivors, Please (1964)

A race of aliens from Rigel, a star located in the constellation of Orion, want to expand to Earth. They plan to eliminate Earth's population by triggering a nuclear war. They take over the bodies of important humans shortly after arranging for their deaths. They occupy U.S. senator Bruns, U.S. ambassador John Farnsworth, Russian General Roskovski, and German rocketry scientist Hans Walter. The policy for all other humans in the replacement "accidents" is: No survivors, please. Howard Moore, a sharp reporter, recognizes the coincidence of miraculous survivals of important people and starts hounding Farnsworth and his secretary, Ginny Desmond, to uncover what kind of plot is involved. The alien boss realizes he is onto their plot and tries to arrange for his body to be added to their collection. While the replacements are good, they do retain a bit of underlying human emotions, especially love. Every time the boss's sniper is ready to shoot Howard, Farnsworth steps in the line of fire. Howard and Desmond fall in love while he enlists her aid in his investigation. The aliens finally get him. He manages to retain and plant a message with Ginny that short circuits Farnsworth's orders to have Walter start the war.