The St. Lawrence River begins where the Great Lakes end, and joins the Ottawa River 200 kilometres into the journey to the Atlantic Ocean. The Great Lakes have cleansed the water above Montreal, but the city's sewage and runoff from roads and factories rapidly degrade the river. The decline in the river continues - heavy concentrations of agricultural pollutants flow in from tributaries below Montreal. Lac Champlain is a dying lake - a recreational paradise now often deserted due to water quality so degraded by intensive farming that beaches were recently closed. Further down river, we examine other human impacts. Why do beluga whales in the lower St. Lawrence have such high contamination of their body fat? What are we doing wrong in the St. Lawrence River?