On a mountain hiking trip at Mystery Mountain, Wendy, Marvin and Wonder Dog discover a giant metallic "U". After reporting their findings to the Super Friends, the junior members show Batman & Robin the exact location where they saw the "U". The caped Crusaders find Dr. Simian Shamon magnetically pulling down a meteorite of solid gold using his "Shamon U". The junior Super Friends stumble upon Dr. Simian Shamon's lab and discover his plans to use his "Shamon U" to mine the skies for gold meteorites. Dr. Shamon refuses to let the Junior Super Friends go or listen to his assistant Madam Lila LaBeau, causing Madam LaBeau to get the young heroes to safety. However, the after-effects of Dr. Shamon's sky mining caused a green and red mist called Shamonite which caused animals, plants, and non-organic objects to either grow or shrink respectively including Wonder Dog. The Super Friends and Madam LaBeau must find a way to cancel out the Shamonite in Earth's atmosphere.