Each year tiny sandpipers -- red knots -- undertake a near miraculous 19,000 mile journey from one end of the earth to the other and back. In this firsthand account, Deborah Cramer accompanies them on their extraordinary odyssey along the length of two continents, tracking birds from remote Tierra del Fuego to the icy Arctic. On the full moon of spring's highest tides, she seeks out horseshoe crabs -- ancient, primordial animals whose eggs are essential to migrating shorebirds, and whose blue blood, unbeknownst to most people, safeguards human health. The Narrow Edge offers unique insight into how the lives of humans, red knots and horseshoe crabs are intertwined. It is an inspiring portrait of loss and resilience, of the tenacity of birds, and the courage of the many people who bird by bird and beach by beach, keep red knots flying.