Eleven-year-old Sebby has found the perfect escape from his crummy house and bickering family--a secret cave he calls "The Hole in the Wall." He discovers this astonishing cave in a pristine, beautiful glen in the midst of a devastated mining area behind his home. But it's not long after Sebby's found it that his world starts falling apart: His family's chickens disappear, colors start jumping off the wall and coming to life, and after sneaking a taste of raw cookie dough he finds himself with the mother of all stomachaches. When Sebby sets out to solve these mysteries, he and his twin sister Barbie get caught in a wild chase through the tunnels and caverns around The Hole in the Wall--all leading them to the mining activities of one Stanley Odum, the hometown astrophysicist who's buying up all the land behind Sebby's home. Exactly what is Mr. Odum mining in his secret facility, and does it have anything to do with the mystery of the lost chickens and Sebby's stomachache? The answers to these questions go much further than the twins ever imagined.