The Case of the Madcap Modiste

This episode emphasized the partnership that Perry and Della have. They traded some zingers and she even provided Perry's "Aha!" moment as he was struggling with the case.

The setting for the action was a design house owned by Charles and Flavia. There were lots of sketches and models wearing high-fashion gowns backstage. The Academy Award-winning costumer Charles Le Maire was credited with the special fashions and sketches. There was no actual fashion show, however, thanks to the murder of the designer just before curtain time. An unusual feature was that we saw the victim die and she gasped out the name of her killer before she succumbed (poisoning).

The lieutenant is quizzing his prime suspect about contact with the victim just prior to her death.
Tragg: She just came in to pass the time of day?
Charles: She was my wife and we talk once in a while.

Later in the holding cell, Perry is talking with his client and Charles doesn't want to discuss some aspects of his personal life.
PM:  The first thing an attorney gives a client is faith. In return for that he expects the truth.

The prosecutor (Les Tremayne of radio fame) for this episode played it as a lark. He’d lean on the armrest of the witness stand in a chatty way and prompt his witnesses. “Go on.” “Anything else?” Just a casual conversation between buddies. At one point he and his witness (the victim’s brother) were shooting the breeze and the judge had to intervene and tell them to “never mind the levity – this is serious business.”

The give-and-take between Perry and Della was a highlight for me.
PM: Della.
DS: Hmm?
PM: Della, think like a woman for a moment.
DS: I’ll try.
During a discussion of the dead designing woman, Perry, Paul and Della try to determine a motive either for her murder or her suicide.
DS: She’s the most inconsistent woman in the world.
PM: Where’d you pick that up? Radar?
Della says she could tell by looking at the current design catalog. The show featured 41 items of clothing that follow of a theme and then the 42nd doesn’t fit in it all. 
PM: Reason?
DS: Her deep-seated inconsistency.
PM: You mean she was a normal woman?
DS: I’ll try to overlook that.