If you can post a summary of that story on to here, then maybe I could help. I haven't read that story, so I have co clue about its major and minor themes.
.......The unnamed narrator laments that he is “sick unto death” after agents of the Spanish Inquisition in Toledo used torture while questioning him. When they unbind him, they allow him to sit while robed judges sentence him to death. Thereafter he cannot make out what they are saying; he can hear only a low hum while their lips move with “immoveable resolution.”
.......In the apartment where he sits, the slight movement of the black draperies unnerves him, but seven burning candles hearten him, like rescuing angels, until nausea overcomes him as he realizes the hopelessness of his predicament. He begins to long for the “sweet rest there must be in the grave.” Suddenly, the judges disappear, the candles go out, and darkness and stillness prevail.
.......He had passed out, he says. When he awakens, he remembers that tall figures had carried him down to a place of flatness, dampness, and madness. He is lying on his back in darkness, wondering where he is–in a dungeon to await public execution? On the very day of his trial, an execution had taken place. Rising, he feels around in all directions, perspiring heavily from fear, and looks for a single ray of light. But there is only the darkness. He recalls ghastly stories about the fates of Inquisition victims held in Toledo dungeons. Would he be starved to death–or worse? This much he could be sure of: Death awaited him. His hands find a wall. He wanders around the dungeon on its wet, slippery floor, feeling as he goes and calculating distances, to determine the size and layout of the place. After he stumbles and falls, he does not get up but instead falls asleep.
.......When he awakens, he finds bread and water next to him. He eats and drinks eagerly. Then he resumes walking and feeling, determining that the perimeter of his cell measures 50 yards. Such information holds no hope of benefiting him, but out of curiosity he continues to find out more. While walking around the cell, he again loses his footing on the slimy floor and falls, ending up at the edge of a circular pit. When he gropes at the edge, a loose rock tumbles into the chasm, sending back echoes after it strikes walls and splashes into water. A door opens and closes overhead, admitting light to the cell for a few seconds.
.......The narrator is now extremely anxious; even the sound of his own voice frightens him. He crawls back to a wall and remains there, fearing that there could be other pits in the dungeon. After several hours, he falls asleep again. Upon awakening, he again finds bread and water. Terribly thirsty, he gulps down the water. When he feels suddenly drowsy, he assumes the water contained a drug. He sleeps a long time. When he wakes up, a sulfurous light enables him to see his chamber–only about half as big as he thought. He attributes his error in calculating its size to unwittingly counting his steps twice. Also, contrary to his earlier conclusion that his cell had an irregular shape, he discovers that it is square. He also discovers that the walls are made of iron plates, not masonry. On the walls are frightful sights: “Figures of fiends in aspects of menace, with skeleton forms, and other more really fearful images. . . .” In the center of the floor is the pit–as it turns out, the only one in the cell.
.......As he observes his surroundings, the narrator is lying strapped to a board so that he can move only his head and his left arm, which he uses to eat food from a dish set next to him. Because the food is highly salted, he becomes very thirsty. But this time, there is no water provided to quench his thirst.
.......The ceiling of the cell is extremely high–between 30 and 40 feet. On it he sees a personified painting of Time. But instead of holding a scythe, as in the traditional depictions, Time is holding a pendulum like the ones on clocks. Something strange then happens: The pendulum begins to swing slowly. The narrator becomes frightened at first, but then loses interest in the sight and shifts his attention elsewhere–in particular to huge rats coming up from the pit, apparently after detecting the presence of the narrator through their keen sense of smell.
.......“It required much effort and attention to scare them away,” the narrator says.
.......He again looks up and notices that the pendulum is descending–and sweeping back and forth at a great speed. The bob of the pendulum is a crescent blade of gleaming steel. As the pendulum swings, it makes a hissing sound. For many hours–for many days–the pendulum descends, getting so close that the narrator can feel it fanning him and smell the odor of the steel. Suddenly, he becomes calm and accepts his fate.
.......Then he faints. When he opens his eyes, he has no idea how long he has been unconscious. However, the pendulum has descended no further. Raging hunger overcomes him, and he snatches up a morsel left by the rats. For a moment, he becomes hopeful.
.......Unfortunately, the pendulum resumes its descent. It is aimed at his heart. When it is three inches above him, he struggles violently. Then he has new hope: Would the pendulum cut the strap binding him? It was a single, continuous length of material enveloping him in all directions.
.......Meanwhile, rats are swarming around him, apparently waiting for his death. He wonders, "To what food have they been accustomed in the well?" They nip at his left hand, seeking the spicy residue of the food he had eaten. This activity gives him an idea, one that could save his life. He passes his fingers across the food dish to pick up oily food remnants and spices, then rubs his bindings with his fingers. A moment later, the rats are upon him–and soon nip and bite through the bindings. He is free!
.......After he slides off the board, the pendulum stops swinging, and, the narrator says, “I beheld it drawn up, by some invisible force, through the ceiling.” Apparently, he concludes, someone has been watching him. Did he escape the pendulum only to be subjected to another form of torture?
.......At that moment, he notices that the sulfurous light in the cell is coming through a fissure running around the base of the walls. He also notices that the images on the wall are now staring at him with fiery demonic eyes and that the smell of hot metal has invaded the cell. It is the iron walls; they are heating up. To avoid the intense heat, he moves to the edge of the pit. Because of the glare from the hot ceiling, he is able to see to the bottom of the well. The sight “burned itself in upon my shuddering reason. Oh! for a voice to speak– oh! horror!–oh! any horror but this! With a shriek, I rushed from the margin, and buried my face in my hands–weeping bitterly.”
.......As the heat in the cell increases, the walls begin to close in, apparently to force him into the pit, and burn his his back. At the edge of the pit, he looks away and waits for the end. Then he hears the blare of trumpets, the hum of voices, and the grating of the walls. They are moving back! Just as begins to fall into the pit, an arm reaches down and pulls him to safety. His rescuer is General Lasalle, of the French army. The French forces–enemies of the Inquisition–have invaded Toledo and taken control
The theme of this story would be the horror torture and being at the mercy of cruel people.