Peter Gunn's friend Doc Clipp has taken up a hobby in retirement, making counterfeits of old stamps for his own enjoyment. This draws the attention of both the Stamp Dealers Association, which offers him $10,000 to stop making the copies, and a counterfeiting gang, which abducts him and wants him to make fake stamps for them to peddle.; Peter and Edie are on their way to see a client of Peter's when they are forced off the road by a purple car. Peter and Edie are picked up by Lt. Jacoby, who is then called to a big chemical plant fire. The plant's owner Jason Colby says his former partner Porter Brandon is responsible for the fire. A plant guard says a purple car was seen going from the plant right before the fire. Gunn checks out Brandon's car, but it's green, not purple. However Gunn catches Brandon in a lie while questioning him and has to find evidence linking him to the purple car.