LONDON — I don’t know about you, but I find dinner conversations often veer in strange directions these days, like the friend telling me the other evening that the terrorists calling themselves Islamic State could easily dispatch one of their own to West Africa, make sure he contracts Ebola, then get him onto the London Underground or the Paris Metro or the New York subway, squeezed up against plenty of other folk at rush hour, and bingo!

“I mean,” he said, “I can’t possibly be the first to have thought of this. It’s easy. They want to commit suicide anyway, right?”

Right: We are vulnerable, less safe than we thought.

A mouthful of pasta and on he went about how the time has come to blow up the entire Middle East, it’s done for, finished; and how crazy the energy market is right now with the Saudis trying to drive down prices in order to make costly American shale oil production less viable, which in turn should ensure the United States continues to buy Saudi crude even now that it has become the world’s largest oil producer.

But of course the Russians are not happy about cheap oil, nor are the Iranians, and the bottom line is it’s chaos out there, sharks devouring one another. Nothing happens by chance, certainly not a 25 percent drop in oil prices. Somebody would pay for this plot.