Hello, first forum post on my part (kicks training wheels off to side).
A couple of the posts in this thread sound eerily like the experience I had with my brother in law, who had a late blooming complex of mental illness take him down completely. When I first met him, he was in his late 30's, successful enough to afford a nice home, had a family, etc. etc., but I did notice he had a tendency to speak about "them" when discussing misfortunes on his and other people's parts, though the identities of "them" was never explored in any great detail. After a few years, his life began unravelling - his occupation as a commodities trader suffered some sizable financial losses, which he began covering by just plain legal theft (draining his wife's money from the joint savings account, convincing other people to loan him money by promising them a high return on their investment ). After a divorce, which he used to sell his home and keep the money from the sale, and several other stunts which he remedied by going to live (read; hide) with his ill parents, he began manipulating them for funds for his trading ventures. It all ended up very badly for everyone in the family - he was conning other relatives, drained his parent's savings, manipulated them into making him the executor of their estate. When all was said and done, he had misappropriated a very large amount of money, created a LOT of discord between all the people involved (which I know now served, unintendedly or not, the purpose of keeping people divided enough that they wouldn't compare notes on his behavior), and still ended up without two quarters to rub together. He had lost it ALL on the commodities exchange.
As it turned out, he was later diagnosed with manic depression and associated paranoia by a court ordered psychiatric evaluation. He had, as you might guess, attracted the attention of several authorities in his schemes. While awaiting trial, he lived at another sibling's house, where he would quite often get into lengthy discussions about how "they" had messed him up at every turn, "they" had sicced the authorities on him, "they" had sabotaged his trading deals. Exactly who "they" were, was never really established, though I think "they" were the usual suspects.
In the end, after serving a prison sentence, he found just about every door closed to him. He ended up going back to the town of his upbringing, where we maintain a second home, which he broke into several times and lived there until we would come and take him to nearby group living homes for people with mental illnesses. When he would leave, we would find a lot of weird arrangement of furniture and household items (candelabras all hidden away, etc.) including - classically - a small room lined with whatever aluminum foil and plastic sheets he could find. After we were forced to get a restraining order to keep him from THAT house, he took to life on the streets of a nearby larger town - where he died at age 54, bundled in a sleeping bag on the steps of a public building. To this day my wife still feels regret that we could not do more for him.
Anyway, hope this isn't just some unloading on my part, but my advice is to keep an eye on people showing consistent signs of mental illness, and try to get them to deal with it - something we never could do with my BIL.