This story in a sense is very similar to another of Poe's famous tales, "The Tell-Tale Heart", because both feature a murder who has concealed their victim, and both include a scene where policemen come into the very room where the body is concealed, and some madness or twist of fate causes the murderer to reveal their crime to those present.
Certainly then if you are focussing on suspense, the end of the story is to me the most suspenseful. Note how, "in a frenzy of bravado", the narrator raps heavily with his cane on the portion of the wall behind which the corpse of his wife lay buried. His hubris however is met with terror. Note how he describes what occurred next:
But may God shield and deliver me from the fangs of the Arch-Fiend! No sooner has the reverberation of my blows sunk into silence, than I was answered by a voice from within the tomb!
This point therefore is the most suspenseful because we are left to imagine what on earth is making that noise - is it the wife who perhaps has not died, or is undead? Or what figure could it be? It is only when the policemen break down the wall that the narrator reveals that the black cat, which seems to epitomise the curse on his life, has been buried with the corpse and it is the cat that gave him away.
The suspense in the narrative of Edgar Allan Poe's "The Black Cat" begins with the narrator's declaration that he will die on the following day.
In the exposition of this story, the narrator proposes to put before his audience what he calls a series of "mere household events." Nonetheless, suspense is generated in the next sentence as he declares that these events "have terrified, have tortured, have destroyed me," and they have produced horror in his mind, although they may be nothing but "natural causes and effects" to someone else.
As the story continues, the narrator admits that he began to drink heavily, and he underwent a personality transformation. For instance, he spoke cruelly to his wife, and he even committed acts of violence against her. The narrator mentions that he had a cat named Pluto with which he established a "friendship." At first, he did not harm the cat, but after the "fury of a demon instantly possessed [him]," he took the poor cat by the throat and cut one of its eyes out of the socket. Later on, he hanged it by the neck.
"...with tears streaming from my eyes...I knew that it had loved me and given me no reason of offense--hung it because I knew that in so doing I was committing a sin, a deadly sin that would so jeopardize my immortal soul...beyond the reach of the infinite mercy of...God."
After his house strangely caught fire that night, the narrator saw that a crowd gathered around "a dense wall" of the house. When the narrator approached this wall, he discovered "in bas-relief upon the white surface, the figure of a gigantic cat...with a rope around the animal's neck." Haunted by this vision of the cat, the narrator discovered another cat who closely resembled Pluto. He offered to pay for the cat, but the landlord replied that he had never seen it before. Oddly enough, the cat followed him home. However, the narrator soon developed an aversion to this cat because he discovered that this feline, like Pluto, was missing an eye. Ironically, the more the narrator was repulsed by the cat, the more fond of the narrator the cat became. Strangely, too, the few white hairs on the cat's chest increased until they resembled a gallows, an ominous thing. At this point the reader wonders about the significance of these occurrences, and more suspense is generated.
One day the cat followed the narrator down steep steps, tripping him and enraging him. He lifted an axe to kill it, but his wife reached up and stayed his hand. Furious that she interfered, the narrator "buried the axe in her brain." Then he tried to hide the woman's body by walling it up in the cellar. Of course, the reader is in suspense, wondering what will happen next.
After this burial, the narrator seeks the cat, but it is nowhere to be found. When it fails to appear, the narrator feels his "future felicity is finally secure." After four days, the police appear. Making a careful inspection of the house, they descend into the cellar. The narrator watches with a calm heart as the police examine the cellar. In an act of bravado, the narrator points to the walls as well-constructed, pounding on those that are directly in front of his wife's dead body. Suddenly there is a "howl, a wailing shriek, half of horror and half in triumph." For an instant, those on the stairs stand motionless. Then, "a dozen arms tear at the wall" until the wife's corpse falls forward. Upon its head sits the cat that the narrator says "seduced me into murder, and whose informing voice had consigned me to the hangman."