The plot

In my opinion, the structure of the story is revealed through the following elements which define the peculiarities of the plot:

Initial situation. The reader meets the narrator and gets to know that he is waiting for death penalty because of some reasons and events which have influenced the story-teller greatly. 
Exposition. The narrator tells the story of his chilldhood and describes himself being kind and always cheerful, but the situation changed when he became addicted to alcohol and cruel towars animals his wife and he kept.
Complication. The main character kills his once beloved cat, Pluto, by hanging him up on the tree in his garden. 
Climax. The fire destroys the house of the narrator at night. His wife, a servant and he manage to escape but now the family is in poverty and they have to change residence. 
Suspence. Another cat appears in the story who is like a living copy of Pluto. The narrator brings him home but gradually the cat gets on his nerves (which are alredy shattered by alcohol).
Denoument. The main character decides to kill the cat but his wife tries to protect the poor animal. She manages to do that but the axe is turned on her. The narrator walls up the dead body and feels happy abou the fact the cat left his home.
Conclusion. Policemen find the body due to the cat whose cry they hear behind the bricks. Thus it turns out that the cat has been walled up too. 

So, there are 7 elements in the plot structure of the story.