Starman is mystified when he discovers crooks who are invisible in ordinary light, but soon learns of the man behind it: a man who is bitter at the government for rejecting his inviso-solution!; Rex Tyler, while delivering chemicals to the Meade Crop Dusters, discovers that boys from the State Reform School are being send to the company to learn trades. However, Hourman discovers that the boys are being made to fly the crop dusting planes themselves, some dying in fatal crashes.; An evil professor succeeds in creating Serum One, a formula that compresses the atoms of the body, reducing it in size, and he uses that ability to not only carry out crime after crime, but to shrink the Sandman in the process so that he cannot interfer!