So many of the Hercule Poirot novels (and Miss Marple too!)depend upon the setting to contain the story. Often, Christie puts her characters in a small village, brings them into a closed suite of rooms, or, most legendarily, puts them on a train.
Let's look at the pros and cons of this closed-circuit kind of setting:
This tight use of setting means that the suspect pool is limited to the group originally introduced to the reader. There are no off-scene murderers in Christie. Which is what makes her cool. To avoid the deus ex machina sensation that accompanies the solution to a lot of mystery novels, a good use of setting seems valuable.
Setting in a particular place requires that the scenes are automatically related. It creates a flow.
Speaking of flow--it also dodges the sometimes tedious descriptions of place. You only have to describe the Orient Express once. (And, if you're Christie, you only have to draw a diagram of the scene once.)
Details stick out, and therefore are given more weight than if the setting were all the details of the wide world. Dizzying. Significance matters in the details. Whether genre or literary...Emma Donoghue's Room was heightened by the details of her small setting in much the same way that Murder on the Orient Express is heightened by the alibi details of the suspects. The reader notices what wouldn't otherwise be noticed.
It can be claustrophobic. Especially in some of the exotic/historical locations that Christie utilizes, it could be disappointing to the reader to not learn more about such locales.
It's very limiting. There are only so many small town/train/plane/automobile areas, right? And once you've established the setting, the characters have to logically fit into the time and place you've set up. So it limits your characters, it limits the scope (it's really hard to get an FBI agent in there if you need to).
Can you guys think of any other pros/cons to a tight setting?
And now, to entertain you, observe the setting of Agatha Christie's legendary Orient Express take off from the station: