During the golden age of mysteries, a great many of the stories were (of necessity) set against the backdrop of drastic changes in society. These changes often provided motives as well as opportunities for the murders. Motives would often be the desire for money to be used on something other than maintaining the vestiges of an old way of life that the new generation is not interested in. The opportunity provided is often along the lines of a large house with few people in them. It’s that latter part that really interests me at the moment.
Large, derelict houses make great settings for mysteries, and I think that this is especially the case in mysteries for children. Scooby Doo was very frequently set in large houses with few people in them, isolated from their neighbors by large plots of land. These are things that most easily happen when societal changes make things that had been popular, or at least populous, less so. When things get abandoned, or even just partially abandoned, there become the remnants of things that people used to do without there being the people around to explain what they were. This makes such a setting is intrinsically mysterious. Whatever crimes a villain is currently committing, there are many things that need an explanation but without the people present who know what they are to give the explanation. Figuring them out, then figuring out which of these is innocuous and which nefarious can provide a wealth of things for the detective to use his intellect on.
This scope for investigation provided by the former scene of a bustling community now in some state of abandonment can be amplified by the intertwining of the current mystery with previous events. This can take the form of treasure which can be discovered or inherited, but it can also take the form of the deeds or misdeeds of the past influencing revenge in the present. It can take the form of both, separately or intertwining.
So how do we make use of this in contemporary murder mysteries? (I mean, murder mysteries set in at least approximately the time of their writing, as opposed to historical murder mysteries.) Many of the social changes which formed fertile ground for Golden Age murder mysteries are, in the twenty first century, over. The remnants of the medieval system are now pretty much entirely gone in England and, to the degree that the southern plantations and robber barons of the United States formed some counterpart, they’re gone too. We still have billionaires, of course, but for a variety of reasons they have fewer servants. (Part of this is technology, part of it is a more efficient economic system where things like cleaning and landscaping are more efficiently done by companies with specialized equipment who service multiple clients.) Even where a billionaire has something potentially interesting like a hundred million dollar yacht, the things are all new. An American billionaire’s household was assembled fairly recently. The odds are pretty good that his house was built fairly recently. The odds of a billionaire’s parents being billionaires is… not high. There are wealthy families, of course, and some of them even have history. I think these can work for this kind of murder mystery—the wealth of wealthy families tends to substantially diminish with each generation. There are exceptions, of course, but children are so frequently different from their parents that it’s rare for the grandchildren of someone who built up a fortune to have even a quarter of their grandfather’s talent for making money, and even less of his being in the right place at the right time to take advantage of that talent.
I suspect that there is more, in the contemporary United States, that can be made of institutions falling on hard times. That happens in all ages, but especially in our contemporary industrial times. Businesses, schools, hospitals, and more go out of business all the time; plenty come close to it or shrink before they’re bought out by competitors. Not every business would be ripe for this kind of setting, but I suspect a lot would. If one couples this with the advisability of Fun Settings for a Murder Mystery, there’s a lot of fertile ground, here.