The lowest and vilest alleys of London do not present a more dreadful record of sin than does the smiling and beautiful countryside.

The remark overturns a common Victorian moral geography that associated cities—especially London’s slums—with vice, while treating the countryside as naturally wholesome. By insisting that “smiling and beautiful” rural landscapes can conceal an equally “dreadful record of sin,” the speaker warns against judging morality by appearances or setting. The line also reflects a recurrent Doyle theme: evil is not confined to obvious, sensational places but can thrive behind respectability, tradition, and pastoral charm. As a piece of social observation, it suggests that crime and cruelty are human constants, merely differently disguised, and that sentimental idealization of rural life can be a dangerous form of blindness.