The characters are:
John and Minnie Wright: John's murder (his wife is the main suspect) is what sets the story in motion. Neither of them actually appear in the story.
Martha Hale: The only character to appear in the entire story, she is sympathetic to Minnie and helps conceal evidence.
Sheriff Peters: The lawman who wants to close the case and doesn't listen to the women in the story.
Peters' Wife: She is also sympathetic to Minnie Wright and helps Martha.
Lewis Hale: Considered the principal witness, he also misses clues as to what really happened.
George Henderson: He is the lawyer whose job it is to convict Mrs. Wright.