The Last of the Really Great Whangdoodles

Three siblings, Ben, Tom, and Melinda Potter (better known as Lindy), meet Professor Savant while visiting the zoo one rainy day. On Halloween, Lindy gets dared by her brother to knock on the spookiest house on the block for a quarter, which happens to belong to the Professor, and the three become more acquainted with him. After a second meeting, they begin spending time at the Professor's house, where he introduces them to games of concentration and observation. He reveals that there is a magic land called Whangdoodleland that can only be reached through the imagination, and that he is training them to accompany him there.

Whangdoodleland is the home of the last Whangdoodle that lived in the world. Once the Whangdoodle, and other creatures that are now considered imaginary, lived in our world. However, fearing that people were losing their imaginations in the pursuit of power and greed, the Whangdoodle created a magic and peaceful world over which he reigns. The professor and the children explore this world.

Each time the children return, they venture farther and farther into Whangdoodleland, intending to reach the palace where the Last Whangdoodle resides. However, the Whangdoodle's Prime Minister, the "Oily Prock", does not want them to disturb His Highness, and sets up a number of traps, both in Whangdoodleland and the real world to prevent this meeting. He enlists the marvelous and funny creatures of the land in his effort, including the High Behind Splintercat, the Sidewinders, the Oinck, the Gazooks, the Tree Squeaks, and the Swamp Gaboons. The children use their imaginations, intelligence, and the friendship of another denizen, the Whiffle Bird, to outwit the traps.

The kids at last meet the last Whangdoodle. It turns out he wants a female Whangdoodle to be his queen, so he won't be lonely, and Professor Savant's knowledge and talents have the ability to grant the Whangdoodle just that. That is, if the Professor can figure out exactly how to do it.