It is up to Beppo the super-monkey, the Wonder Twins, and Gleek to stop Gorilla Grodd from ruining a carnival that has come to Metropolis.

Because his own mother is too young to take care of him, Umande, a newborn gorilla, is fed and cuddled by human zookeepers until a surrogate mother is found.

When a priceless yellow diamond is stolen from the museum, Superman, Batman, and the other Super Friends follow the clues and discover that Gorilla Grodd is using the diamond to create an army of yellow gorillas.