Originally Aired: September 14, 1948
Philo Vance #10, "The Blue Lady Murder Case," a mysterious and dangerous woman known only as "the lady in blue" arrives in town, and her reputation for bringing trouble—killings, bank holdups, and kidnappings—precedes her. District Attorney Markham summons detective Philo Vance to his locked office, where informer Ricker warns them about this tall, dark, striking woman who always wears blue. The lady in blue wastes no time forcing her way into the local rackets, confronting gangster Danny Claxton and demanding to be his partner. When Danny refuses, violence erupts as her bodyguard Tony shoots Danny in the arm.
Undeterred, the lady in blue continues her campaign, targeting Madame Marie's dress shop and demanding a percentage of all purchases. She manipulates Danny by playing on his attraction to her, but when he tries to get physical, she slaps him and humiliates him. Danny swears revenge, but before he can act, he's found murdered—stabbed in his own apartment. Now Philo Vance and Sergeant Heath must unravel whether the beautiful woman in blue is a cold-blooded killer or something more complex.