Lyric discussion by RaweGenar 

Cover art for The Missing McCloud Boys lyrics by Prize Fighter Inferno

I dont think it's Arthur McCloud telling this one because he dies in "Our darling daughter you are little Cecilia Marie". I think it's Martha McCloud finding out what happened to her sons and blaming herself for not solving the puzzle earlier (like stated above). She turns to god to avenge the murderers of her sons. This song is clearly about revenge.