A mysterious extraterrestrial race, simply referred to as the Alien Visitors, comes to Earth to perform a genetic experiment of monumental proportions upon the human population. The Aliens arrive in the midst of an air battle over Germany during World War II, abducting B-17 pilot Captain Russell Keys and his entire crew. Russell loses all memory of the incident, retires a highly-decorated war hero, settles down with his childhood sweetheart Kate, and has a son named Jesse. Eventually, Russell realizes he is still periodically being abducted and, desperate for answers, tracks down the sole surviving member of his bomber crew, Lieutenant Lou Johnson. Johnson, in his final moments, makes him realize the "German doctors" experimenting on them were Aliens using their abilities to disguise themselves. Not wanting to bring the Aliens down upon them, he abandons his family and flees for his life. Meanwhile, in Roswell, New Mexico, Captain Owen Crawford discovers a crashed saucer, which is soon retrieved and becomes the initial subject of a "Project" intent on discovering the Alien Visitors' purpose on Earth, which is headed by Colonel Thomas Campbell, Owen's superior. After Owen is frozen out of the investigation, he is given a mysterious Alien Artifact, seduces and marries Anne, daughter of Colonel Campbell, and uses both the artifact and the marriage to blackmail Colonel Campbell. He gets promoted to Major and becomes leader of the Project. Owen attempts to locate the fifth member and only survivor of the spaceship crew. This alien, in human disguise and calling himself "John", enjoys a relationship with the lonely Sally Clarke, who sheltered him (despite learning of his true nature) and ended up pregnant by him.