This is a synopsis of the script. Horacke Blake is a banker; Ellen his 19-year-old daughter; Archie Windsor is a wealthy playboy; Leon Selby is Windsor's secretary and cousin, and Mr. Saunders is the manager of a jewelry shop.
The episode opens with Lamont and Margot taking a walk in the park. They find Blake in the park, having been hit by Archie. Blake is angry at Archie since he has designs on his daughter.
Selby and Archie talk, Archie pointing out that a $10,000 pearl necklace he bought for Ellen is now missing. He accuses Selby of taking the pearls and replacing them with fakes. Selby kills Archie with a knife.
Selby calls Blake and imitates Archie's voice, saying Ellen is at his place. He then calls the police and tells them about a body, hoping to set up Blake as Archie's murderer.
Lamont and Margot arrive and find the body. The police arrive and Blake is arrested. Ellen comes to them later and asks for their help is proving her father's innocence. Selby arrives and talks to Ellen and Lamont.
Ellen is left along with Selby, and she realizes Selby is behind everything. Lamong and Margot check out the jewelry shop, and find out Archie had returned the necklace. Margot and Lamont go to his apartment to consider what has been happening. Ellen manages to get to a phone and calls Lamont.
Margot goes to talk to Selby, and Margot says that she has realized that Selby is the murderer. Suddenly the voice of the Shadow is heard. The Shadow reveals that Selby used his acting experience to impersonate Archie when he returned the necklace. Selby tries to use a knife but the Shadow stops him.
Then it's later and Lamont and Margot are talking. The police have arrested Selby, and Lamont recounts how he investigated Selby and determined his guilt.