This is a short story collection (not too short) and the title piece is the first one and the immortal lines there might be trouble to which the reply “trouble is my business” is uttered.
Highlights from the first half of Trouble is my business
* Private eye John Dalmas is hired to try and get a wealthy man’s son away from a relationship with a woman that has connections with a gambler that the young man owes money to
* Dalmas is sub-contracted from another investigator that hasn’t got the energy to pursue the case and he is referred to the other detective who she had hired to work on collecting background
"I need a man good-looking enough to pick up a dame with a sense of class, but he's got to be tough enough to swap punches with a power shovel."
* The other detective turns up dead and that forces Dalmas to get acquainted with the main characters more quickly than he might have chosen to and he is rewarded with being knocked down out by the gambling son
* On returning home two men with guns are waiting for Dalmas and they warn him off the case but fail to give any other information leaving the detective intrigued about all the fuss that is being made