There is a definite man-versus-man conflict in "The Adventure of the Speckled Band." Helen Stoner comes to Sherlock Holmes for help and advice because she is afraid someone is trying to kill her. She believes this because that night she had heard a low whistle exactly like the one her sister Julia had told her about two years earlier, just before her sister died of unknown causes. Helen tells Holmes a long back story which gives the detective some clues. But he feels it is necessary to come to Stoke Moran to inspect the premises. It seems significant that Helen's stepfather Dr. Grimesby Roylott has just made her move into the bedroom directly next to his, the room that had been occupied by Julia Stoner until her death.
Shortly after Helen leaves, her angry, violent stepfather bursts into Holmes' and Watson' sitting room, demanding to know why Helen had been there. Holmes coldly refuses to tell him. Roylott becomes further enraged. The following excerpt is intended to establish that the conflict is between Sherlock Holmes and Dr. Roylott.
“I will go when I have said my say. Don't you dare to meddle with my affairs. I know that Miss Stoner has been here. I traced her! I am a dangerous man to fall foul of! See here.” He stepped swiftly forward, seized the poker, and bent it into a curve with his huge brown hands.
“See that you keep yourself out of my grip,” he snarled, and hurling the twisted poker into the fireplace he strode out of the room.
Disregarding Roylott's warning, Holmes, accompanied by Watson, goes down to Stoke Moran that very afternoon. He examines Helen's bedroom and Dr. Roylott's bedroom next door. He sees enough to satisfy him that Roylott is trying to kill Helen to prevent her from getting married, in which case he would have to pay his stepdaughter a substantial annual sum from her mother's estate. Holmes and Watson spend the night in Helen's bedroom. When they hear the low whistle at three o'clock in the morning, Holmes strikes a light and sees the "speckled band," which is a deadly poisonous snake trained by Roylott to crawl through the ventilator and down onto the bed. This was obviously the way Roylott killed Helen's twin sister Julia two years ago when she occupied this room. Holmes drives the snake back up the bell-pull and through the ventilator. The angered snake bites Dr. Roylott, and Holmes and Watson find him dead.
Thus the conflict between Holmes and Roylott, man-versus-man, is resolved when Holmes kills Roylott with his own poisonous snake. At the very end of the story the author, Arthur Conan Doyle, uses the following comments by Holmes to show that the conflict in "The Adventure of the Speckled Band" was indeed between Holmes and Dr. Grimesby Roylott. Roylott wanted to kill Helen; Holmes wanted to protect her. Holmes tells Watson:
"Some of the blows of my cane came home and roused its snakish temper, so that it flew upon the first person it saw. In this way I am no doubt indirectly responsible for Dr. Grimesby Roylott's death, and I cannot say that it is likely to weigh very heavily upon my conscience.”