The Old Man in the Corner by Baroness Emma Orczy

The mysteries themselves are typical of Edwardian crime fiction, resting on a solid foundation of unhappy marriages and the inequitable division of family property. Other aspects of the time are illustrated by a murder in the London underground system; murder of a female doctor; and two cases involving artists living in "bohemian" lodgings. Another new and noteworthy feature of these cases: no one is ever brought to justice, and in fact most of the villains cannot be proven guilty beyond a reasonable doubt.