Lord Peter Wimsey, while staying at an inn, finds a stranger is completely rapt in reading and rereading from a book of Wimsey's. It turns out to be H G Wells' story of a man inverted via the fourth dimension, The Plattner Experiment [sic]. The stranger finds himself identifying with Plattner's situation, because he is convinced something similar has in fact happened to him, right down to right-left internal organ inversion. Lord Peter listens to the man's unusual story with polite interest. But soon afterwords, when he learns that the man is wanted for murder, Lord Peter embarks on finding a three dimensional explanation of the past events in order to exonerate him in the present."