I read this book about 1-Apr-2015. I've read this book before. The book is copyright 1930. This note was last modified Sunday, 10-May-2015 18:07:06 PDT.
This is book 6 of the "Lord Peter Wimsey" series.
This note contains spoilers for the book.
Harriet's origin story (in the series), and Peter immediately forms the goal of marrying her.
And it's pretty clear that, without Peter's interference, Harriet would have been wrongfully convicted and hanged. Nobody would ever find out what really happened, short of the actual killer making a deathbed confession or something.
The basic story is Urquardt having played fast and loose with a client's money, and needing to kill the heir to hide the fact that there's nothing to inherit.
The client is a senile old woman who was a notorious (and very successful) actress, and got quite rich at it. Wimsey sends in Miss Climpson, and we have her reports of seances with the nurse caring for the old woman. A will has been faked, and Urquardt overplays his hand a bit in attempting to convince Peter that the will is real, which makes him suspicious.
This is probably the book that most brought to public knowledge the fact that one can acquire a tolerance to arsenic.