Planning to return to Earth after their adventures on Mars, Flint and Mimi are approached by Princess Viga, who begs them to stay and help defend her people from a terrifying monster.; Cole is ordered to take a large fleet to the Planet Zog to take on a giant who is extracting tribute from Zog's poor people.; Professor Sandow detects strange flashes among the clouds, so Payson and Roland investigate, and discover a castle on a cloud, where they discover eerie Hawkmen who seek help in eliminating a war between the clouds!; Spurt is sent to the planet Venus in order to obtain a supply of Radia-Tronite crystal which is needed to supply power to America's generators, leading to a war between America and Mars.; Buzz, the doctor and his daughter are attacked by mysterious Crab-Men at the bottom of the seas covering Neptune, are captured and taken to the lair of the evil Sinfo, who controls the creatures, and who intends to use his captaives as guinea pigs.; At one of his famed gigantic banquets, Auro is pulled aside by one of the servants, Ava, and told that he must flee before the murderer of her parents, Agra, arrives to kill him.; Tiger Hart rescues the captive Queen Hilda from the clutches of Turk the Terrible, who is holding her in exchange for the Great Solinoor diamond.