Adapted from a novel by Chicagoan Sam Greenlee, The Spook Who Sat By the Door (1973) stands as one of the most unlikely movies ever made in America and by far the smartest, most daring of the blaxploitation films. The protagonist, a social worker recruited by the CIA as a token black, uses his espionage training to launch a revolution on the south side. Producer-director Ivan Dixon was denied shooting permits by the city and had to stage the climactic riot sequence in Gary. But he did manage to steal some run-and-gun footage around Chicago, most notably along the Green Line at the King Drive and Cottage Grove stations. The movie opened to great business but quickly disappeared, allegedly because the distributor and exhibitors were pressured by the FBI. Dixon preserved the negative only by storing it under another title, and the movie wasn't widely available until a DVD release in 2004.