Clark Kent is traveling in a cab which is hit by a rival cab driver. When he questions the driver, he says that the rival driver is a member of the Cab Protective League, an organization that victimizes independent cab companies.

As Superman, he travels to the independent Carlyle Cab Company. He discovers the boss being threatened by a member of the CPL. He reveals himself and beats up the racketeer. He picks him up and leaps into the air. The racketeer tries to stab him, causing Superman to crash into a building, leading the racketeer to fall to his death.

Mr. Reynolds, the boss of the CPL calls Mr. Carlyle and asks whether he's going to pay for protection. Carlyle refuses, so he and his henchmen go to confront him. Superman destroys their car, and also makes them all destroy their own cabs. Superman also makes Reynolds confess to ordering the deaths of other drivers, and he gets arrested.

As the police drive him to the station, he lights a cigarette. The cops realize too late that the cigarette contains a poison gas. Superman finds an abandoned police car right where the police were last seen. He hurtles through the roof of the cabin, where he finds Mr. Reynolds. Reynolds introduces him to his boss, the Ultra-Humanite, the most intelligent man on earth. Superman approaches the Ultra-Humanite and is caught in a wave of electricity that temporarily knocks him out. The Ultra-Humanite quickly has Superman tied to a board that is being cut with a saw.

But of course the saw blades have no effect on Superman. In fact, one of the blades breaks off and kills Mr. Reynolds. The Ultra-Humanite calls some henchman, who carry his paralyzed body away to a nearby plane and start the cabin on fire. Superman wakes up and escapes the cabin just before the fire can kill him. He crashes into the Ultra-Humanite's plane, destroying it. However, the Ultra-Humanite's body is nowhere to be found...

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