The final lines hint at the "brotherhood" of Dupin and D----. Earlier, Dupin says their minds are alike. In what ways are Dupin and D---- doubles of one another?

G. R. Thompson notes that Dupin's "role . . . is complex and suspect," and that he is set up as "a godlike omniscience, with the 'I' narrator and the reader playing the role of the dull-witted dupes." Furthermore, Thompson notes that "Dupin and D—. . . are moral doubles, each having a talent for duplicity and malice," and that "Dupin's interest in the case is morally dubious."