After living on the Fog Mound for quite some time, Thelonious Chipmunk and his friends are ready to continue their travels. There are still old questions to be answered and new places to be explored. So, with the addition of new friends Bill the Human and Cluid Chipmunk, the animals sail off down the river in a specially designed boat.

At the City of Ruins they find the dangerous ratminks threatening to take over the region and maybe even the whole planet! Could this be a repeat of the events that brought about the end of the Human Occupation? How can one small group of talking animals help? Why is Bill so anxious to get to the mysterious island of Faradawn? And will Olive find her lost sister, Ruby?

As in Travels of Thelonious, the intrepid chipmunk pursues his personal quest to uncover the differences between legend and history. And to answer the most troubling question of all -- what happened to the humans?