Everything comes in circles. [...] The old wheel turns, and the same spoke comes up. It's all been done before, and will be again. - Arthur Conan Doyle

"What is the meaning of it, Watson? said Holmes solemnly as he laid down the paper. "What object is served by this circle of misery and violence and fear? It must tend to some end, or else our universe is ruled by chance, which is unthinkable. But what end? There is the great standing perennial problem to which human reason is as far from an answer as ever.

Now, Watson,” said Holmes, as a tall dog-cart dashed up through the gloom, throwing out two golden tunnels of yellow light from its side lanterns. “You’ll come with me, won’t you?”
“If I can be of use.”
“Oh, a trusty comrade is always of use; and a chronicler still more so. My room at The Cedars is a double-bedded one.

It is a mistake to confound strangeness with mystery. The most commonplace crime is often the most mysterious because it presents no new or special features from which deductions may be drawn. This murder would have been infinitely more difficult to unravel had the body of the victim been simply found lying in the roadway without any of those outré and sensational accompaniments which have rendered it remarkable. These strange details, far from making the case more difficult, have really had the effect of making it less so.