Here's why:
* Holmes's Deductive Reasoning: Holmes uses his exceptional powers of observation and deduction to unravel the mystery of the speckled band and the method of Dr. Roylott's murder attempt. He meticulously analyzes the clues, connecting seemingly unrelated details to expose the killer's plan.
* Dr. Roylott's Deviousness: Dr. Roylott is a master of deception, employing cunning strategies to conceal his murderous intentions. He manipulates his environment, uses fear and intimidation, and even attempts to frame an innocent party to divert suspicion.
The story becomes a battle of wits between these two figures: Holmes's sharp mind against Dr. Roylott's carefully laid traps. The tension arises from the uncertainty of whether Holmes can decipher the puzzle in time to save the victim.