From The Perry Mason TV Show Book
In this episode, Perry proves at last that murder is no laughing matter.

A judge asks Perry to defend a self-destructive young woman named Carla Chaney, who is being held for the murder of Gerald Havens, a smalltime art critic. The woman has led a troubled life and refuses to trust anyone. It’s not surprising that no one believes her story about the fatal night when Havens was stabbed to death. Carla claims she saw a woman standing over the body laughing in a high-pitched, maniacal tone. Moreover, later Carla says she saw the woman on television during the grand opening of the Devore Gallery. The other woman is Leona Devore, a well-known member of the jet set.

Through it all, Perry believes Carla. To get her acquitted, he has to find out who really did the laughing.