Captain Marvel investigates reports of a strange little man carrying a small black bag, selling fire insurance. When a business fails to buy it, a strange arsonist appears on the scene and sets the place on fire.; Sivana uses his latest discovery to shrink Captain Marvel and Beautia in size, landing them in a microscopic world, where they face an array of dangers.......including Sivana himself.; Mr. Morris sends Billy out to discover the truth behind the strange murder of a poor sailor, and Billy finds himself shanghaied aboard the pirate ship "Sea Witch", heading for an isolated island where the Captain of the ship seeks the sunken treasure of Tamungu just off shore.; Captain Marvel battles the Spider Men from Mars, who have invaded the Earth, and whom, he discovers, are robots!