Could it be that Godman was innocent and someone doesn't want Stafford to rake the case up? Detective Pitt investigates Stafford's death (with the help of his wife Charlotte as usual). Pitt questions persons of interest, makes observations, consults with relevant lawyers and judges, and so on.
My problem with the book is that too many characters repeat the same evidence/story ad infinitum which becomes long and tedious. The book could have been edited to be a third shorter without losing any important threads. Also, a number of characters spout anti-Semitic sentiments, which I found offensive but is probably authentic for the time period.
Overall, it's a decent mystery with plenty of memorable (if not particularly likable) characters. The book's resolution was surprising but believable. In any case it's always fun to read the author's depiction of the rigid customs, foibles, and hoity-toity attitudes of the British 'upper classes' of the 1800s.