When an injured diamond dog finds himself in Canterlot, he informs the ponies of the terrible new monsters his brethren have uncovered in the Macintosh Hills. In response, both the princesses sent a three pony reconnaissance team to investigate the dog's claim. What started out as a simple mission will soon turn disastrous when Captain Path Finder and his two troops, will find themselves lost in the underground maze beneath the mountain. And to make things worse, they are being hunted by the very monsters the dog spoke of.