 Kurt Gerstein, a brilliant German scientist, is recruited into the SS during the opening years of the Second World War. Assigned as a sanitation engineer, Gerstein is sent to the Eastern Front to supervise water purification for the German Army. Soon after, however, he is asked to help with a "special project" involving fumigation of "vermin infested" areas behind the front lines. Gerstein develops Zyklon-B, a deadly chemical gas which Gerstein believes will be put to use killing rats, lice, and other disease carrying creatures. However, when Gerstein realizes that his invention will be used to kill not animals but people, he begins an emotional search of his Christian values and ultimately decides to betray the SS by attempting to expose the Holocaust by way of informing the Catholic Church.