The film is based on the 1842 short story with the same title by Edgar Allan Poe.
He is thrown into a dark, subterranean room, where he gropes about and discovers that a deep pit yawns in the center of the floor.
When unseen eyes observe that he has not stumbled into it, guards enter the dungeon and place him on a low bed, to which he is tied down, supine, the long surcingle wrapped tight across his body [to immobilize him].
Left alone in this position, looking up toward the ceiling, he beholds a descending pendulum with a crescent blade of steel.
The prisoner takes some meat from a bowl near the bed and smears the surcingle that binds his chest.