In early 1942, shortly after the United States entered World War II, President Franklin Roosevelt received an alarming intelligence report: Germany and Japan were developing biological weapons for potential offensive use. In response, the U.S. and its allies rushed to develop their own germ warfare program, enlisting some of America's most promising scientists in the effort. This program examines the international race to develop biological weapons in the 1940s and 1950s, revealing the scientific and technical challenges scientists faced and the moral dilemmas posed by their eventual success. As America's germ warfare program expanded during the Cold War, scientists began to conduct their own covert tests on human volunteers. The United States continued the development and stockpiling of biological weapons until President Nixon terminated the program in 1969. "Biological weapons have massive, unpredictable, and potentially uncontrollable consequences," he told the nation. "Mankind already carries in its hands too many of the seeds of its own destruction."