Despite the fact that thousands of pounds are offered for Sir Danvers' murderer, Scotland Yard receives no information. Seemingly, Hyde has vanished. Yet, if the man himself has disappeared, past stories about him continue to surface. More tales about his past acts of cruelty are uncovered, and a general sense of Hyde's vile and violent life remains. But, as for the man Hyde, it is as though Jekyll was right: Hyde seems to have permanently left his quarters in Soho (then, a down-and-out, bohemian section of London) and escaped — never to be heard of again.
Coincidentally, just as the disappearance of Hyde seems to be a matter of fact, Jekyll's sanity and his sense of good health return. The doctor comes out of his self-imposed seclusion and begins giving dinner parties again. He is seen often in public, and people take note of how happy and healthy he looks. For two months, it seems as though Dr. Jekyll immensely enjoys life once more.
Yet, on January 8, Utterson dined with Jekyll, and only four days after this festive and merry dinner party, Utterson goes to see his old friend and is turned away by Poole. Likewise, he is turned away several more times. Utterson becomes concerned. He had come to believe that both Jekyll's mental and physical health had returned to him. But now it seems that Jekyll has lapsed into a grave illness that threatens both his body and his soul. For that reason, Utterson hurries off to see Dr. Lanyon.
He is relieved to find that the doctor is at home, but when he sees Lanyon, he is stunned to discover that his old friend is terribly ill. Lanyon "had his death-warrant written legibly upon his face."
Utterson senses that Lanyon, however, is not dying of physical decay; it seems as though he is a victim of some "deep-seated terror" within his mind. Utterson cannot help himself; he remarks on how very ill Lanyon looks, and the doctor admits that indeed, he is seriously ill. "I have had a shock," he tells Utterson, and when Utterson mentions their friend Jekyll's similar illness, Lanyon's face changes. He says that he never wishes to see or talk about Dr. Jekyll. He is vehement: He is done with the doctor; from now on, he will regard Jekyll as being already dead.
Utterson protests at such a display of hatred, but Lanyon is firm. He never wants to see Jekyll again. He tells Utterson that perhaps someday Utterson will learn about the "right and wrong of this." The phrase "of this" eludes Utterson; he cannot fathom what Lanyon is referring to, but whatever "this" may be, it is sufficient to cause Lanyon to tell Utterson that if he cannot talk about a subject other than Jekyll, he must leave.
When Utterson returns home, he sits down and writes a letter to Jekyll, asking straightforwardly for an answer about why he and Lanyon have quarreled. The following day, he receives Jekyll's answer. But after reading the doctor's letter, Utterson knows no more than he did formerly.
Jekyll shares Lanyon's view that the two old friends must never meet again. As for himself, Jekyll says that he intends to lead a very secluded life from now on. However, he pleads with Utterson to believe in Jekyll's genuine friendship for him, but he asks Utterson to trust him to know what is best for all concerned. "I have to go my own dark way," Jekyll says, and it is a way that Utterson must not try and follow. He says further that he has brought a terrible punishment and a danger on himself; he never imagined that he could, or would, become "the chief of sinners," or that the earth contained such "sufferings and terrors"; he begs Utterson to respect his fervent wish for absolute privacy and solitude.
The lawyer's worst fears are confirmed. The old "dark influence" has returned and enveloped Jekyll; only a few weeks ago, it seemed impossible — Jekyll had seemed to be healthy and cheerful. Now, all that has changed, and what is more, Jekyll has condemned himself to a living hell. Utterson is tempted to diagnose the malady as simply madness, but because of Lanyon's frenzied condemnation of Dr. Jekyll and because of his ambiguity about his reasons for hating Jekyll so thoroughly, surely it is more than simple madness which now consumes Jekyll. There must be something else.
Less than three weeks later, Lanyon is dead. After the funeral, Utterson returns home and goes to his business office; there, by candlelight, he takes out a sealed envelope and studies it. Written on the outside of the envelope is: "PRIVATE: for the hands of G. J. Utterson Alone, and in case of his predecease to be destroyed unread." The emphasis on these last two words puzzles Utterson. Reluctantly, he decides to open the envelope. Within, there is another envelope, also sealed, with instructions "not to be opened till the death or disappearance of Dr. Henry Jekyll."
Utterson's mind reels; the same phrase that he read in Jekyll's will, "death or disappearance," confronts him anew, flooding him with black, sinister waves of revulsion for Edward Hyde. Without a doubt, Lanyon's writing is on both envelopes, and thus the mystery concerning Hyde, Jekyll, and Lanyon mounts, and as much as Utterson longs to solve the mystery once and for all, he cannot betray his old friend's honor and faith. Thus, he replaces the inner envelope into the outer envelope and replaces both of them in his safe once again. Then he goes to Jekyll's apartment, but Poole has unpleasant news. The doctor, he says, lives almost continually alone in the single, small room over the laboratory; he does not read, and he says very little. Something terrible seems to be preying on his mind.
Utterson continues to return to Jekyll's quarters, but each time, Poole has the same melancholy news: Jekyll is living alone above the laboratory and seeing no one. Thus, Utterson's futile visits become fewer and fewer.
At the opening of the Chapter, when the police are investigating Hyde's life and deeds, and we hear about the numerous vile practices he has committed, we now realize that during the year that elapses between Chapters 3 and 4, Hyde had apparently practiced every type of vile and violent deed and "had collected a multitude of enemies." This causes Utterson to utter "the death of Sir Danvers was . . . more than paid for by the disappearance of Mr. Hyde." This is not a callous statement when we realize the extreme extent of the evil practiced by Hyde. Utterson is the type who would gladly sacrifice a single life if it insured the riddance of a universal evil which Hyde now appears to be.
It is also symbolic that once Dr. Jekyll has rejected Hyde, Jekyll changes completely. In medical terms, he has purged himself of some deep disease that was eating away at him. With Hyde gone, for some time (Sir Danvers was murdered by Hyde in October, and it is now early January), Jekyll has changed back into his old social self and has been a delightful host. Thus, it is even more puzzling when Jekyll suddenly reverts to his old secretive self. The explanation for this episode is not given until Chapter 10, when Jekyll explains that he was sitting in Regent's Park, when suddenly, to his horror, he became Edward Hyde and found himself clad in the over-sized clothes of Dr. Jekyll. The shock of this transformation occurring without the use of his potion causes the doctor to totally isolate himself.
During Utterson's visit to Dr. Lanyon, he discovers the man to be the victim of some unknown terror which has literally announced his doom — he will be dead in three weeks. What Utterson or the reader does not know is that by the chronological time of Utterson's conversation with Lanyon, Dr. Lanyon has already been exposed to the events narrated in his document that we will read in Chapter 9. That is, on the 8th of January, Utterson had dined with Dr. Jekyll and yet it is only two days later when Lanyon received the letter from Jekyll, dated January 10th, begging for help, and it was then that Lanyon was exposed to the fact that Jekyll and Hyde are the same. We do not know this until later, but the novel is already looking forward to that knowledge, and we can now understand Dr. Lanyon's total collapse.
The cause of Lanyon's death — the horror — is not fully clear until the entire novel is considered. It must be remembered that both men had once been very close friends and that both men are eminent in their professions. Likewise, we ultimately know that Dr. Lanyon has disapproved of Dr. Jekyll on professional grounds — that Jekyll's metaphysical speculations about human behavior transcend the true limits of physical medicine, that Dr. Jekyll's ideas are "too fanciful" for him, and thus they broke company. However, no matter how metaphysical or fanciful Dr. Jekyll's ideas are, when Dr. Lanyon was exposed to the reality of the speculations in the person of Hyde, who before Lanyon's eyes became Jekyll, it horrifies him. The actual horror of the discovery that Jekyll and Hyde are one person lies not in the discovery itself, but in the full realization concerning the nature of evil in all men. The effect of Lanyon's being exposed directly to EVIL INCARNATE is simply too monstrous for Dr. Lanyon to absorb, admit, or handle because this would mean that every person, including Dr. Lanyon, is partly evil. The shock of this realization therefore kills him. A similar type of idea is found earlier in the century in Nathaniel Hawthorne's story "Young Goodman Brown"; Brown went forth into the forest, where he had a vision of evil, in which he saw all of the good ministers and goodwomen and even his wife, Faith, in secret conspiracy with the Devil. After that night, Young Goodman Brown was forever a changed and gloomy man. A direct confrontation with the personification of evil in the person of Edward Hyde and his transformation back into Jekyll was simply more than the good Dr. Lanyon could handle.
Utterson's character is put to a test in this Chapter. Upon Dr. Lanyon's death and the receipt of the envelope with the instructions "not to be opened till the death or disappearance of Dr. Henry Jekyll," Utterson is sore put not to obey his friend's request.
Having lost one friend, Dr. Lanyon, and fearing the loss of Dr. Jekyll because of the strange wording "death or disappearance" — the same words Jekyll used in his will — all of these things combine to tempt Utterson to violate Lanyon's trust and open the envelope, especially since it might contain some information which might help save Dr. Jekyll. But "professional honor and faith to his dead friend" restrain him from opening the envelope, which he locks away in his safe.