Who is/are the main character(s)?

Narrator ("The Tell-Tale Heart")

The murderer of the old man who claims he is hypersensitive rather than insane. He cannot stand the old man's eye, which prompts the killing. Although he goes about the murder very carefully and systematically, he is driven to distraction by the sound of the dead man's beating heart.

Old man ("The Tell-Tale Heart")

An unsuspecting man who treats the narrator of "The Tell-Tale Heart" well, but nevertheless drives his companion to murder.

Policemen ("The Tell-Tale Heart")

The three men who come to the murderer's house to investigate a shriek heard in the night. Unsuspecting, they sit down with the murderer for a chat before the latter shows his hand.