“Thunder in Guyana” profiles Janet Rosenberg Jagan, the Chicago native who served as president of the small South American nation from 1997 to 1999. Jagan, who succeeded her husband, Guyanese progressive icon Cheddi Jagan upon his death, followed him to his homeland in 1943, and their story----told by her mother's cousin, filmmaker Suzanne Wasserman---is one of idealism and struggle. “Maybe it's boastful,” Jagan says sweetly, “but I would define myself as a freedom fighter.”