What does an eleven-year-old boy do when he learns of a subterranean world? If he is adventurous and imaginative, he sets out to find it of course; and that is just what Ian Lawrence does. After solving the Portal's secret, he enters the strange, but wonderful world of Arboritia. An amusing meeting with a Woodin named Bunkin draws him into an adventure he never expected. He learns of the theft of a special wand tip from a wondrous wand belonging to the unusual Snake Wizard, Snuggly P. Wigglesworth, and the effect this act will have on the Aboritian forest. The boy designs and helps the troubled Woodin community construct a hot air balloon based on Ian's class science project. The balloon takes Ian, Bunkin and a Woodin huntsman, Senic, over Turquoise Lake to Shrouded Mountain. On the mountain's forbidding, fog-covered plateau they encounter many dangerous obstacles among which are fogworms, mire pots, polymorphs, genyxs, and xordions. But their greatest challenge is the Gnobblin thief and rogue, Naggins, who gives the reader a humorous encounter with his own guardsmen; and the frightening creature called Abominus, who stands in the way to Turquoise Lake and home.