1947 also had B-noirs!

From Gord's IMDB review:
This one is a Republic Pictures quickie with the always ravishing, Adele Mara, as a private-eye. Mara played many a damsel in distress, femme fatale or general all round babe in 60 films between 1941 and 1950. Here, in a real change of pace role, Mara plays a female version of a hard-boiled, wise cracking private detective.

A rich industrialist type, Russell Hicks, pays Mara a visit at her office looking for a P.I. Though somewhat at a loss for words after discovering the detective is a woman, he hires her. Hicks explains that he thinks his step-son Mark Roberts might be in some sort of trouble. Roberts is withdrawing large amounts of cash from the family business without any explanation.

Mara agrees to take the job and arranges to meet Roberts at Hick's home that afternoon. When she arrives, there is a more than slight problem, Hicks has been murdered. The Police are summoned and the Inspector assigned turns out to be Mara's father, Robert Armstrong. Armstrong of course is not at all pleased with daughter Mara's choice of profession.

Suspects and red herrings abound as Mara and her assistant William Hadde, sift through the clues. In the mix beside Roberts, is his sister, Adrian Booth, the butler, Harry Shannon, the family doctor, Colin Campbell, the shady company lawyer, Charles Evans, the ex-business partner, Paul Burns, gangster, Bob Steele and Edward Gargan as a less than helpful drunk.

Everyone seems to have a motive for the killing, or at least for helping to cover for the killer. Who did, or is going to do what, to who, is the theme here. First the coroner says it is murder, then suicide, then a heart attack and finally back to murder. There are plenty of snappy lines traded here between Mara and the various suspects.

Adele Mara was married for just under fifty years to novelist-screenwriter-producer Roy Huggins (who needs no introduction)...