Dude Donaldson dresses as a rodeo clown, he and an accomplice rob a rodeo brutally killing half-a-dozen people. Cannon is summoned to figure out what's going on, after authorites spend 6 weeks and come up with nothing. There's a home movie taken at the time of the robbery, in the vicinity of the buliding and Cannon and the others watch this film over and over, like the Zapruder film, and eventually it dawns on Cannon that the clowns may be involved. He tracks a clown suit to a Texan who died in Vietnam the previous winter to the man's widow who is less than forthcoming. Her young son gives Cannon some leads including that the suit was taken from the widow's barn and used in the robbery. Dude goes to Glenda's house and threatens her and her son against saying anything to Cannon. Cannon senses what's going on, and after almost being shot by Dude, he subdues him with a bear hug.