Solve my Murder Mystery Plot
I just want to see how obvious my murder mystery plot is, and see how I can make it better. Yes, it uses cliché tropes intentionally, critique those too.
Plot: we are introduced to our characters as they board first class on a train and gossip amongst each other in the dining car. Much of the talk is about the stock broker (M39) obviously flirting with a baroness (F57).
It also becomes apparent that the other passengers previously knew of this broker; one had their father go bankrupt investing with him, another is an agent sent by a bank that he is heavily in debt to, yet another lost his job to the broker, etc.
During the night, a rough patch of rail shakes the train, during which a small caliber shot is fired, barely heard, and dismissed. In the morning, the broker is found dead having been shot. A detective on board questions them, and not one passenger is surprised.
The suspects are narrowed down to someone with a gun, and who likely knew about the rough patch of rail to cover the shot. The baroness has a small Derringer pistol and frequents the train route, but is the only passenger aboard that was fond of the broker. The baroness' maid is a suspect as she had access to the pistol and traveled the route with her before.
The possible answers are obvious when worded like this, but if there's any other twists that I could add, I'd be happy to hear them. Maybe another person aboard had planned to kill him, but was beaten to it?