How could the loss of just one single species matter? Against a backdrop of dramatic and colorful artwork, this book tells the story of Dr. Robert T. Paine's landmark research on ochre sea stars. His study revealed that the presence or absence of one single species can affect an entire ecosystem. The main story introduces readers to intertidal life along the Pacific coast while describing the steps of Paine's research. Gradually revealing the connections that tie together the existence of many diverse species in this tumultuous ecosystem, the book clearly conveys the surprising importance of one individual species. Through the story and extensive back matter, readers learn about ecology, keystone species, and the invisible connections that exist everywhere in nature.