In the third book of this series, Zoey and Sassafras head to the stream only to make a terrible discovery. Things get even more urgent when they learn that the magical creatures living in the stream are in danger! Can Zoey and Sassafras solve the mystery of the stream and save the Merhorses?

Each story in the Zoey and Sassafras series features a new magical animal with a problem that must be solved using science. There isn't a set formula for each book; Zoey sometimes needs to run experiments, while other times she needs to investigate a mystery, and yet other times she needs to do research. Zoey models how to keep a science journal through her handwritten entries in each story. Each story is complete with a glossary of the kid-friendly definitions for scientific terms used. The series highlights child-led inquiry science and the topics covered align with both Common Core and Next Generation Science Standards.