From The Perry Mason TV Show Book
The office of a South African diamond company located in the same building as Perry’s office is robbed and the suspect matches the description of a typist who spent some time working in Perry's office. This is just the beginning of a series of strange events that leads Perry into the courtroom defending Duane Jefferson for murder.
When the jury brings in a verdict of guilty, Burger believes he finally has a victory over Mason. It looks that way until we realize that the defendant is an imposter.