Dr. Henry Jekyll is a complicated character, though readers don't get a full picture of him until he explains his deeds and choices in the final chapter. Like all humans Henry Jekyll is, as he puts it, a "composite." His nature is both good and evil, civilized and primitive. Intrigued by this dual nature and wanting to experience the two separately, Jekyll finds a way to indulge his darker passions without it becoming known. Jekyll applies his knowledge of chemistry and invents a "tincture" that separates his good from his evil identity and even creates an entirely different body for each self. (Edward Hyde is his evil persona.) Above all Jekyll is almost classically arrogant. He believes he can reconstruct his own identity in order to break humanity's shared ethical rules and England's social norms, and without paying a price. Obviously he is wrong, and this novella is an account of his errors and how he pays for them.
Edward Hyde is the evil side of Dr. Jekyll's identity. He came into being when Jekyll invented a drug that would split his good and bad natures into two entities. Hyde even possesses a different body than does Jekyll. Hyde is younger than Jekyll but also hairier, as if he is more primitive. He is full of energy and is more evil than Jekyll's dark side had been. Everyone who sees Hyde finds him disturbing, but no one can name a single specific detail that makes him repellent. There's something about him that seems less evolved, like a caveman, but also something that seems purely evil. Hyde and Jekyll share a single memory. At first Jekyll must use the "tincture" he has created to transform himself into Jekyll, but after a while Jekyll finds himself transforming into Hyde spontaneously, first while he's sleeping and then while he's awake.
The interplay between Dr. Jekyll and Mr. Hyde is the engine driving this story. However, by the end, both of the two interwoven characters are dead. Mr. Utterson is the closest thing in the novella to a unifying consciousness or point-of-view character. Utterson is a lawyer and brings a lawyer's seriousness and logic to his interactions with other characters. Utterson is always aware of his responsibilities. At times, as when he's talking with Poole, he even warns people about this responsibility. However, Utterson's seriousness goes beyond his professional capacities. He is an austere man who actively practices discipline and resists temptations, even in his private life. This is most visible in the novella's opening paragraph. Utterson actively denies himself the things he enjoys, like drinking wine and going to the theater, precisely because he enjoys them. In this way he, more than Jekyll, is an anti-Hyde. Whereas Jekyll created Hyde to give his passions free rein, Utterson always holds a tight grip on his own actions and feelings.
Richard Enfield is one of several examples of Victorian respectability in this story. He is related to Utterson ("a distant kinsman"), and, though he is not nearly as austere as Utterson, he values their time together considerably. This kinship is literal, but it is also symbolic: these men align with virtue and civic duty, unlike Hyde. The two men take walks together every Sunday. It's on one of these that Enfield tells Utterson the "story of the door," which starts the narrative of Hyde (and Utterson's interest in him) in motion. Enfield's curiosity draws Utterson's attention to that mysterious door—and the reader is drawn in as well. Enfield is also Utterson's companion for the "incident at the window," when Jekyll must disappear because he's losing control to Hyde. Enfield functions as a witness to extraordinary events.
Dr. Lanyon is introduced in the second chapter when Utterson is searching for Mr. Hyde. He's important for several reasons. First, as Utterson notes, Lanyon is another of Jekyll's old friends. Their relationship deteriorates throughout the novella, which helps build dramatic tension. Second, Utterson is a lawyer, and his rejection of Hyde might be colored by that professional perspective. However, Lanyon is a doctor and so is qualified to evaluate Jekyll's project from a scientific perspective. Tellingly, he calls Jekyll's research "unscientific balderdash." Third, the story's sixth chapter focuses on Lanyon and the change in his health and relationship to Jekyll, though the meaning of that chapter is not revealed until the novella's ninth chapter, "Dr. Lanyon's Narrative." That later chapter reveals what Lanyon went through earlier: he saw Hyde change into Jekyll. This unnatural transformation shook Lanyon's mind and broke his health.
Poole is Jekyll's main servant and has been with the doctor for decades. In some sense, if Jekyll serves as Hyde's public face, Poole serves as Jekyll's public face. When Utterson first visits Jekyll in "Search for Mr. Hyde," he has to ask Poole if Jekyll is home. And Poole makes excuses for him. Once Utterson's relationship with Jekyll deteriorates sufficiently, he actually says he'd rather deal with Poole on Jekyll's doorstep than enter his friend's house. Poole's long service gives his testimony extra weight. His intimate knowledge of Henry Jekyll lets him speak with certainty in "The Last Night" and confirm for Utterson that it isn't Jekyll locked in the lab, but Hyde.
Dr Lanyon is an important character in Stevenson's novel because, like Dr Jekyll, he is a scientist and doctor, so he makes an interesting point of comparison and contrast. He is also the only character to actually witness the transformation of Hyde/Jekyll. His account of this is very interesting to the reader. Stevenson saves Lanyon's account until the penultimate chapter, where it dramatically solves most of the mystery about the character of Mr Hyde. (1 [1: Opening paragraph briefly but clearly focuses upon a) the importance of Lanyon and b) the author's presentation. ])
Dr Lanyon first appears in Chapter 2 when Utterson goes to consult him about the strange will of their friend Dr Jekyll. He is described as a "hearty, healthy" gentleman with a warm manner of welcoming his friend that is based on "genuine feeling". (2 [2: Quotation shows evidence of the first bullet point in the question - what Lanyon is like. ]) This emphasis on his good qualities and his genuine friendship is important. (3 [3: Point. ]) It makes us trust him and believe his judgement may be right when he says that, because Jekyll "began to go wrong", he has seen little of him during the last ten years. In fact, he becomes uncharacteristically agitated and talks angrily of Jekyll's ideas as "scientific balderdash". This raises our level of interest in what Dr Jekyll might be involved in. (4 [4: Comment. ])
Utterson (5 [5: Paragraph focuses on two different characters' reactions to Lanyon - clear focus on the second bullet point. ]) is clearly very friendly with Lanyon, and likes him. Because Utterson appears in the novel much more frequently than the doctor, and is also a steady, reliable, caring man, we tend to trust Lanyon even more. Stevenson makes him appear a model of reliable good sense and decent friendship. Dr Jekyll also tells Utterson that Lanyon is "a good fellow... an excellent fellow". But he adds, "a hide-bound pedant for all that; an ignorant blatant pedant", and scorns Lanyon's disagreement with "what he called my scientific heresies". (6 [6: Quotation provides evidence. ]) This again raises our interest in what Jekyll is up to, because his attitudes toward Lanyon are wildly contradictory. (7 [7: Comment. ])
Up to this point in the novel, Stevenson has made me like and trust Dr Lanyon. He is possibly a bit stuffy (but only possibly - can Jekyll's judgement be trusted?), but his heart is in the right place. In Chapter 6 (Remarkable Incident of Dr Lanyon), however, Stevenson creates a shocking change in Lanyon. When Utterson visits him, he finds a man "with his death warrant written legibly on his face". As a reader, I (8 [8: Use of "me" and "I" shows evidence of personal response, which the third bullet point asks for. ]) am concerned to find out why. But even though there are hints of a dreadful confrontation between him and Jekyll, a horrific mystery hangs over the cause. The previously cheerful scientist and doctor lives in dread, feels he will soon die, and refuses to talk to Utterson about their former friend, Jekyll. His words "if you cannot keep clear of this accursed topic, then in God's name, go" show the author's skill (9 [9: Comments directly on how Stevenson makes you respond to Lanyon, which the third bullet point asks for. ]) in making the reader fascinated by the mystery.
Lanyon is important to the novel (10 [10: Focuses clearly on the fourth bullet point - the examiner can easily follow the structure of your essay. ]) because of the dramatic mystery surrounding what he has seen. It excites the reader and draws us in. He is also important because, as a scientist and doctor, his disagreement with Jekyll's "wrong in the head" (11 [11: Brief quotation. ]) ideas shows us that Jekyll is thinking and working outside of normal science. Jekyll is "breaking the rules", an important theme in the novel which would be far less apparent without the character of Lanyon. (12 [12: Refers to a theme of the novel. ]) In the penultimate chapter, Lanyon's account of what he has witnessed raises the ending of the novel to a fever pitch of horror. Finally, in Lanyon's terrified language, we learn that Hyde is Jekyll and that Lanyon witnessed the transformation - this is why he is important in Stevenson's novel. (13 [13: Focused conclusion returns us to the title. ])