Water's journey from streams entering Lake Superior to the mouth of the Saint Lawrence Seaway takes 350 years. The narration establishes the importance of the Great Lakes for the U.S. and Canada's fresh water. Then, for each of the Great Lakes, plus Lake St. Clair, the film focuses on specific environmental problems: lamprey eels in Lake Superior, heavy metals in Lake Michigan, zebra mussels in Lake Huron, petrochemical waste in Lake Erie, and toxic waste dumps near Lake Ontario all degrade human and animal health. The film argues that governments and industry turn a blind eye to needed clean up and regulation, putting plants, fish, birds, and humans at risk.