In this novel, a ring is 
In this novel, a ring is found in a goldfish pond whose inscription indicates that it is from someone with the initial R. Other clues in this novel include the fact that Charles Kent's last name is also the name of a county and that the parlormaid Ursula has recently given notice, supposedly because she disarranged the papers of the title character. The resolution of the plot in this novel revolves around the overhearing of the sentence "The calls on my purse have been so frequent of late that I fear it is impossible for me to accede to your request," which turns out to have been spoken by a Dictaphone. Ultimately, Ralph Paton, the butler Parker, and the rest of the members of the central household are found to be innocent by Hercule Poirot. For 10 points, name this Agatha Christie mystery in which the murderer is revealed to be James Sheppard, who also happens to be the narrator.
In this novel, a ring is found in a goldfish pond whose inscription indicates that it is from someone with the initial R. Other clues in this novel include the fact that Charles Kent's last name is also the name of a county and that the parlormaid Ursula has recently given notice, supposedly because she disarranged the papers of the title character.
The Murder of Roger Ackroyd