Dan White who portrayed Pop (uncredited) the father of Chief Harry Decken, portrayed by Howard Duff, was only 5 years 8 months older then Howard Duff.
The title is a reference to a line from Shakespeare's Macbeth.
The exploding car stunt went wrong, as recounted in a September 15-21, 1973 TV Guide article titled, "'It Was the Closest I've Ever Come': The Day a Mannix Stunt Went Out of Control." Stuntman Dick Ziker was inside the burning car when a gust of wind fanned the flames, which quickly enveloped him. "The stuntman dove out to save himself, but not before his hair caught fire. ... The stuntman crawled away from the burning car, a bit singed around the edges, but happily far from char broiled. Said a shaken Ziker, "It was the closest I've ever come."