How does Sir Authur Conan Doyle make the reader think Dr. Roylott is the obvious villain?
In the story The Speckled Band, by Sir Arthur Conan Doyle, Dr. Grimesby Roylott is painted as an eccentric man with a short temper. Dr. Roylott is the stepfather of Helen Stoner, who comes to Sherlock Holmes fearing for her life. Helen's sister died several years previous, and the strange circumstances of her death seem to be repeating themselves. Doyle sets up the story so that we suspect Dr. Roylott of attempting to kill his stepdaughter, and concludes with Roylott's plan backfiring- retribution!
We know from Helen's description of her stepfather that Dr. Roylott spent time in India, where he worked as a physician. He now keeps many exotic pets from the subcontinent, including a cheetah and a baboon, who he lets roam the estate at night. Dr. Roylott also spent time in jail after beating his butler to death. When Helen is finished giving her testimonial and departs the home of Mr. Holmes, Dr. Roylott bursts in minutes later and threatens Mr. Holmes and Dr. Watson. He brandishes a fire-poker at them and warns that he is a dangerous man.
Naturally, when Dr. Roylott attempts to discourage Holmes and Watson from looking into Helen's case, we come to suspect he has something to do with the strange events taking place at the estate.