The Uttermost Farthing is a mystery by R. Austin Freeman.
Excerpt from the book:
Humphrey Challoner was a great savant spoiled by untimely wealth. When I knew him he had lapsed into a mere dilettante; at least, so I thought at the time, though subsequent revelations showed him in a rather different light. He had some reputation as a criminal anthropologist and had formerly been well known as a comparative anatomist, but when I made his acquaintance he seemed to be occupied chiefly in making endless additions to the specimens in his private museum. This collection I could never quite understand. It consisted chiefly of human and other mammalian skeletons, all of which presented certain small deviations from the normal; but its object I could never make out—until after his death; and then, indeed, the revelation was a truly astounding one.