The panther's old car breaks down in the middle of the street. Meanwhile, Dr. Jekyll has developed a magic potion which transforms him into the mean Mr. Hyde. He pours the same drink into his car, and it transforms into a big and mean speed machine. He then goes to a used-car salesman and trades in the car for a new one. The salesman intends to sell the old car for a large sum, but when the car transforms back into its old, compact shape, the salesman lowers the price - and that's when the panther notices it. He buys the car, which soon transforms into its fast and dangerous shape. The panther gets chased by the police but manages to escape when the car shape-shifts back into its normal shape. When the car again gets mean, the panther stops the car at the red light, hops out, but gets chased by the car. When the car finally runs out of gas, the panther, relieved, goes into a toy shop to buy himself a scooter.