The day after their return to London the investigators visit Aubrey. He has spent much of the last two weeks working on a sequence of three canvases that show great, if slightly disturbing, promise. Like Georgina, he has experienced troubling dreams. Returning from the visit, Ludwig is greeted by his next-door neighbour, Mrs Grundy. A taxi-driver was asking after his address; he said he had a confused old gentleman in his cab who wanted to see him. Neither the taxi-driver not the old gentleman ever reappear.

Acting on a vague memory, Georgina searches her uncle's papers for references to Hali and Carcosa. She finds a slim privately-published volume titled, in German, "The Wanderer by the Lake". The author is given as "A. R." and the text, a mixture of English and German, matches the style of Alexander's speech. Aubrey, meanwhile, attempts to contact Talbot Estus with a view to borrowing his copy of "The King in Yellow".

Dr Highsmith's letters of introduction produce a quick response. Dr Trollope, the Roby family doctor, is willing to meet the investigators at their convenience. Graham Roby, Alexander's older brother, sees no benefit in an interview but is willing to answer their questions by letter and will ask the police to make details of the murder case available.

The investigators meet Dr Trollope early the next evening. The Doctor, a bachelor in his early sixties, is distinctly Victorian in his attitudes, manner, and taste in interior decor. He seems a little pale and tired, perhaps from overwork. He does not believe in the modern theories of psycho-analysis and does not expect that Alexander will ever be cured. He believes Alexander was a weak man, although fundamentally decent, and the deaths of his father and sister left him broken. Both he and the Roby family considered Alexander's companions unsuitable. Delia was his fiance for a time, although the engagement was broken some months before the murders; he has no knowledge of Edwards or Malcolm Quarrie. Dr Trollope was also one of the first on the scene after the murders; his account matches that of the police, below.

Two days later, Dr Trollope is dead. The investigators read in the papers that he has been fatally stabbed while taking his regular evening walk in St James' Park. His attacker is described as a tall thin man; there may also have been a shorter confederate waiting outside the park. The investigators interview the only witness, a paper-boy. Dr Trollope had a whistle in his hand that he had presumably grabbed from his attacker. The boy took it, but mention of the police is enough to get him to hand it over. The whistle is made of a jet-black substance as light and warm as amber; it takes the form of the elongated head of an unknown creature. Blowing the whistle causes Georgina and Aubrey to feel dizzy for a moment. Their dreams that night are vivid and unsettling.

The investigators contact the police and are interviewed in connection with the murder of Dr Trollope. The investigating officer, Detective Inspector Taylor, is interested in their statements but makes it clear that they are not considered suspects. The next morning they return to New Scotland Yard to speak with Detective Inspector Stevens about the Roby murders. Stevens is busy, and hands them off to a sergeant who gives them a summary of the case files. The two bodies were found in the drawing-room, with signs of a considerable struggle. The father, Herbert, had a single large stab wound by the left collar-bone and the body was entirely drained of blood. The sister, Georgina, had several large slashing wounds from something like an axe; there was evidence of both left-handed and right-handed strikes. The drawing-room door, although unlocked, had been smashed off its hinges. No footprints or fingerprints were found. Alexander was found in his room upstairs, weeping. The glass balcony doors in his room were broken but, again, there were no footprints to suggest an intruder. Despite his insistence that he was responsible, there was no physical evidence linking Alexander to the murders. The investigators request access to the full witness transcripts. This is possible but will take time to arrange, as the files have been archived.

On the morning of the second visit to Scotland Yard, Ludwig receives a letter from Dr Trollope. The letter is dated November 3rd, the day of his death, but was sent on the 6th. In it, Dr Trollope unburdens himself of much that he felt unable to say in the investigators' interview. He believes that Alexander had fallen into bad company and was being used by his companions for some, presumably sinister, end of their own. He believes their names were Edwards, Bacon, and Quarrie. Three years ago Graham Roby hired a private investigator, a Mr Vincent Tuck, to follow Alexander and report on his associates. Perhaps he knows more? Although he shared Graham’s disapproval of Delia, he believes she is innocent; Alexander had broken off their engagement before Mr Tuck's investigation and made no further attempts to contact her. There is one further thing that troubles him. While visiting Alexander in the asylum some six months ago, he read passages out loud from Alexander’s book in the hope of obtaining a reaction. When Alexander joined in the reading, Dr Trollope fell briefly unconscious and experienced a vision of his death – by stabbing, on a winter evening in St. James’ Park.

The investigators pay a visit to Mr Tuck, who has his office in a rather insalubrious part of Wapping. He is happy to assist them, and digs out his files. Lawrence Bacon is a reclusive dealer in antiques and curios; Alexander and the others met regularly at his house. Malcolm Quarrie is a scholar, working at the Royal Society. Edwards is more mysterious; he lived in short-let lodgings and spent most of his time in various libraries around London; Tuck was unable even to learn his first name. Quarrie was perhaps the outsider of the group.  After several steadying drinks, Tuck passes the investigators a report of what happened when he followed Bacon on one of his few excursions. It appears that Bacon killed a tramp without touching him, leaving a mummified corpse. Tuck heard a whistle sound when the killing took place. The investigators hire Tuck to trace Edwards, Quarrie and Delia; he is reluctant to have anything to do with Bacon but will try to arrange a watch on his house.

Georgina and Ludwig attempt to translate "The Wanderer by the Lake" but have little success at first - the author's German is not that of a native-speaker. Aubrey, meanwhile, contacts Talbot Estus through his publisher and arranges a visit. Mr Estus is hard at work on his next novel, to be titled "The Yellow Sign", and his study is a chaotic mass of notes. The notes contain few complete paragraphs, or even sentences, and are becoming illegible under a growing mass of diagrams and annotations. Aubrey gratefully accepts the loan of "The King in Yellow", which Mr Estus feels he has gone beyond, and leaves as soon as politeness allows.

Next session: an interview with Graham Roby and Vincent Tuck's report. There are many clues, but what do they reveal? And there are things, of course, that it is better not to know at all...