In 1942, Robert and Françoise Monier make a hot air balloon to fly to the stratosphere.Before leaving ,the husband has an accident.His wife carries out the experiment with the laboratory assistant.The balloon drags them along towards space ;after a visit to Venus where they meet a couple fluent in French,they land on the good old Earth but,(theory of relativity) they have aged fifteen days whereas on their native planet ,twenty-five years have passed.