Vieux d'un milliard d'années

In 2178, Doctor Fred Gibson is on Jupiter searching for his fiance Elsa. His romantic rival, archaeologist Phil Travis, finds her first but lacks the medical knowledge to treat her properly. Gibson, however, finds ancient Jovian technology that reveals its history: scientist Halfar Kal invented a "Droga Ray" that evolved the Jovians into pure energy, allowing them to travel throughout the galaxy. Gibson uses the ray on himself and as an invisible energy being helps Travis save Elsa. Travis returns to Earth, but the grateful Elsa opts to stay with Gibson, who used the ray to return to normal.