Twelve-year-old Joel Ragsdale is supposed to be looking after his little brother, Benton, at the park. When the two-year-old tumbles into an abnormally large gopher hole, Joel knows his only choice is to follow Benty into the pit where Joel rolls out into an undiscovered world filled with dazzling colors and populated by bizarre creatures. Frantic, Joel must explore this unfamiliar land to locate his brother while fighting off the mutants trying to imprison him. Captured by research scientists Joel battles his terror of being used for experimentation to focus on searching for his brother who might already have fallen victim. Will Joel find his brother in time and escape to get help for the ill-treated prisoners who have spent their lives underground?