Nadine, a young woman, is the perpetual unpaid servant of her rich and unkind uncle. She tells him she is soon to be married and he will need somebody else to tend to his needs. He responds by showing her a copy of something and saying that if she walks out on him he will send that to her fiance. Nadine seems very distraught by this turn of events.
Later, when she visits her fiance's chemistry lab - he's a chemist himself - she steals some cyanide. Her uncle drops dead of cyanide poisoning shortly after she serves him some soup. She has a mental breakdown upon his sudden death, is hospitalized, and confesses to her uncle's murder, although she is in a distressed state. Perry is on the case.
Nadine is made up to be a rather plain young woman. She has a very short haircut that does not complement her and she wears clothes that don't complement her. She seems to have a problem with confidence and with helplessness. But in spite of these issues, her fiance does love her and apparently so does one of the other suspects, to the point that his wife is jealous of her.
This episode was a rather average one for Perry Mason, but even average Perry Mason is good viewing because of the cast. There is one humorous thread I see going on here. In this episode, as in "The Case of the Drowning Duck", Perry has to take a trip to the desert community of Logan City. In both episodes, each time the cast of Perry Mason is visiting there, they frequently wipe their brow with a handkerchief, I guess to underscore that it is hot there, just in case you forget that this is the desert. A rather pedestrian touch made cute by the fact that Perry Mason is usually such a subtle show.