In 1900, Major Walter Reed, Chief Surgeon of the U.S. Army, led a team to Cuba to investigate yellow fever, the disease that had killed an estimated 100,000 people in the US in the 19th century alone. Reed and his team tested the radical theories of Carlos Finlay, a doctor who believed that mosquitoes spread the disease. This program documents the heroic efforts of Reed's team, some of whom put their own lives at risk to verify Finlay's theory.