“FBI agents are some of the most idealistic people you can imagine,” says former G-man Wesley Swearingen in John Edgar Hoover and the Great American Inquisitions, a new video documentary by Chicagoan Denis Mueller. Swearingen says he joined the FBI “to put bank robbers in jail,” but he soon discovered he was mixed up in a clandestine, and often illegal, war against political dissent. “We had a police state,” he admits, “and it was a secret one.”

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Swearingen’s 25-year stint at the agency beginning in the early 1950s required acts of espionage against antiwar and civil rights activists as well as anyone suspected of having ties to the Communist Party. Fellow agents in the Chicago office were asked to spy on religious leaders and educators. These deeds were referred to as “black bag” operations because many agents carried doctors’ satchels with equipment for picking locks, opening mail, and photographing documents.

Hoover’s absurdly autocratic style led to some odd actions. Mueller tells of one agency underling who misconstrued a note about neatness Hoover scribbled on a memo’s margin–“watch the borders”–and he dispatched FBI agents to the Mexican border. Petty high jinks included penning letters to Martin Luther King Jr., calling him an “evil abnormal beast,” and meddling in writer Nelson Algren’s sex life by blocking his travels to Paris to see Simone de Beauvoir.