Just another quiet day in Mammoth Falls. Or is it? Have flying saucers really been sighted? How about those rumblings in the ground during the wee hours of the morning... and a midget submarine hidden in a secret cavern?

With evidence like this, our seven young geniuses can't be far behind. And they're not! The town of Mammoth Falls will never be the same again, because here come the Mad Scientists with five more mad adventures!

Stories in this volume: The Telltale Transmitter, The Cool Cavern, Big Chief Rainmaker, The Flying Sorcerer and The Great Confrontation.