Everything you need to understand or teach Clouds of Witness by Dorothy L. Sayers.
The contrast among Lady Mary's three suitors nicely illustrates an important theme in the book concerning the importance of human life. Her official fiance Denis Cathcart is a jaded illustration of the decadence of the old order. He is seeking a marriage of convenience and wishes to marry only in order to support his mistress in a better style. He is the victim, but as his past is unfolded through detective research, he becomes increasingly less sympathetic, so it is with some relief that readers learn Lady Mary had become disillusioned by his coldness and — finally frightened — had planned to elope with someone else on the very night of Cathcart's death. George Goyles, the alternative lover, turns out, however, to be even less sympathetic than Cathcart. He is a textbook Communist, spouting slogans about the rights of the people but evincing no human understanding of the...