Who are the main characters in "The Adventure of the Speckled Band" by Sir Arthur Conan Doyle?

Two of the main characters are, of course, Sherlock Holmes and Dr. Watson. Sherlock Holmes is a brilliant and highly logical detective, who shows his caring and compassionate side in this story, while Dr. Watson, the story's narrator, is his faithful and less uniquely brilliant sidekick. The other main characters are Helen Stoner and Dr. Grimesby Roylott, her stepfather. Helen Stoner is the good-hearted but badly frightened woman who comes to Holmes for help. She is engaged to be married and is fearful that her stepfather is going to kill her. Even though she can't pay for his services, Holmes feels enough sympathy for her that he takes on her case.
Dr. Roylott is an ill-tempered man whose family estate has fallen on hard times. He had to go to India to earn money but has now returned. He arrives at Holmes's office and in a display of bad temper tells him to stay away from his stepdaughter. He bends one of Holmes's fireplace pokers as a show of strength. Neighbors avoid visiting his estate because of his bad temper and because he lets a cheetah roam his grounds.