In the short story "The Adventure of the Speckled Band" by Sir Arthur Conan Doyle, a woman named Helen Stoner approaches Sherlock Holmes and Dr. Watson in fear that her life is threatened by her stepfather, Dr. Grimesby Roylott, who is a vicious and violent man. Helen is concerned that Dr. Roylott killed her twin sister and now intends to kill her as well. During their conversation, Holmes discovers that Helen has been physically abused by her stepfather. Holmes and Watson plan a visit to Stoke Moran, where Helen lives with Dr. Roylott.

After Helen leaves, Dr. Roylott himself bursts into the room. He is a large man with a threatening demeanor. He refuses to sit down and immediately begins questioning Holmes about Helen's visit. Dr. Roylott demands answers, but Holmes calmly responds by commenting on the weather. He is obviously unwilling to give his unwanted visitor any confidential information. After Roylott calls him a meddler and a busybody, Holmes merely smiles and indirectly suggests that he should leave.

Roylott then warns Holmes to stay out of his affairs, and to illustrate his threat he grabs a metal fireplace poker and bends it into a curve. Roylott leaves after this display. Holmes laughs and tells Watson that even though he is not as big as Roylott, he is also strong. He then picks up the steel poker and straightens it out.

The incident does not intimidate Holmes at all. Instead, he says that it "gives zest to our investigation." In other words, it makes it even more exciting. We see, then, that the visit does not cause Holmes to become frightened so that he drops the case, which was Dr. Roylott's intention, but instead it makes Holmes all the more eager to solve the mystery. Eventually, of course, he does, when he discovers that Roylott released a poisonous snake to kill Helen's sister and then attempts to kill Helen in the same way.

When the furious Dr. Roylott bursts into Holmes's rooms on Baker Street, shouting accusations at him, Holmes responds "blandly." He keeps his emotions in check, mainly ignoring Roylott's ranting accusations. Holmes treats his opponent with amusement and refuses to allow himself to be baited into a sharp response by Roylott's threats.

For example, Holmes responds with laughter to Roylott:

Holmes chuckled heartily. “Your conversation is most entertaining,” said he.

Holmes shows no fear or agitation at the other man, even when Roylott picks up a fireplace poker and bends it to show his great strength. After he is gone, Holmes calmly reveals his own physical strength by bending the poker back into it original shape. He then says to Watson:

Fancy his having the insolence to confound me with the official detective force! This incident gives zest to our investigation, however, and I only trust that our little friend will not suffer from her imprudence in allowing this brute to trace her.

From these words, we see that Holmes reacts to Dr. Roylott as a "brute." The man is an annoyance to him that he holds in contempt, but he also adds "zest" to Holmes' work. Roylott's angry, out of control behavior lends credence to Helen Stoner's fears of being murdered, as she suspects her sister was. We sympathize with her all the more once we witness her nemesis's encounter with Holmes.

It becomes clear that the story will be a battle of wits between the cunning but aggressive Roylott and the intelligent and supremely cool Sherlock Holmes.

Sherlock Holmes and Dr. Roylott only meet in person one time. Dr. Watson is present and describes the meeting. Roylott bursts into Holmes' sitting room and tries to interrogate and intimidate the detective. Holmes is perfectly cool and even mocks the intruder by totally ignoring his questions. For example:

“I am Dr. Grimesby Roylott, of Stoke Moran.”

“Indeed, Doctor,” said Holmes blandly. “Pray take a seat.”

“I will do nothing of the kind. My stepdaughter has been here. I have traced her. What has she been saying to you?”

“It is a little cold for the time of the year,” said Holmes.

“What has she been saying to you?” screamed the old man furiously.

“But I have heard that the crocuses promise well,” continued my companion imperturbably.

Holmes and Watson do not see Dr. Roylott again after he storms out of Holmes' living room until he is dead, having been bitten by his own poisonous snake. It was not absolutely necessary to the story to introduce Dr. Roylott after his stepdaughter Helen leaves. Holmes could have gone down to Stoke Moran, inspected the rooms, waited in the dark with Watson, and driven the "speckled band" back through the ventilator, where it killed its owner--all without ever having met his antagonist while Dr. Roylott was still alive. The purpose of the short and unproductive meeting between Roylott and Holmes was to introduce the element of conflict and drama. The story becomes a conflict between these two strong-willed men, and the menace of Dr. Roylott hangs over the remainder of the story. If this powerful and half-mad man were to catch Holmes and Watson snooping inside his country manor, he is quite capable to trying to kill them. A country gentleman like Roylott would certainly possess an assortment of guns. 

Fortunately, Roylott remains in London for the remainder of the day after threatening Holmes. And when Holmes and Watson see him again that night he is sitting dead. By driving the snake back into Roylott's room, Holmes had settled their conflict by causing the other man's death.

"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.”