Reflecting on the characters discussed thus far, I then sought some further clarification. “Inspector, you have mentioned Flanagan, the concierge, the Godbolds on floor two and Cartwright and his secretary on floor three. But were there any other tenants or visitors in the building that day?”

The answer was again simple and direct. “No, Doctor. That is our entire cast, with the exception of the missing assassin. And if you want my view on how he could have escaped, I would say that it must have been during those first few minutes when the concierge ran up the stairs in response to the shouting of Chester Godbold. Mount told me that when the shot was fired he was in his office and heard only a muffled bang. At first, he believed it had come from the street, but stepped outside the office to listen further. He thought he could hear someone running on the stairs, but could not tell if they were ascending or descending. And as he strained to hear more, was suddenly aware of the cries for help and ran up the stairs to be greeted by the three Godbold brothers in some distress. If our mystery assailant was hidden in one of the washrooms at that time, he could have made his exit from the building shortly afterwards, out of sight of the concierge, and pulling the latch to behind him.”

From what I had heard, I could only concur with the meticulous detective. And seeing that Lestrade looked to be flagging somewhat, I suggested that we take a short break and enjoy a pot of tea and a slice of fruit cake which Mrs Hudson had very kindly prepared for us. For a short while, Lestrade chatted amiably about life at Scotland Yard and some of the other cases he was working on, but within fifteen minutes he had returned to the events at Ravensmere Towers.

“I ought to furnish you with some further information about the two remaining floors of Ravensmere Towers - I know that Mr Holmes is a stickler for detail. The first four upper floors are of a similar layout and design, with the two adjoining rooms being accessed from the main door facing the stairwell and lift area. All contain the same basic items of furniture and are let as furnished offices. The commonality of design extends to the large, potted plants which adorn each office and run down the walls to the left of each of the main office doors.

“Floor four also has a short corridor running from the back room - the one with windows - to a second door, which provides an alternative exit to the lift and stairwell. It sits to the left of the main office door, obscured by the line of potted plants. The top floor is different again, being but a single open office which runs around the lift and stairwell. Mr Cartwright explained that it was designed to be a large storage area for a business venture which needs only to make the most of the space available without any sort of reception area or desk. The room contains just two small filing cabinets.”

“Well, that all seems straightforward, Lestrade. And is there anything further you can tell me about the Godbolds, Mr Cartwright and Miss Trelawney and where they all were when the fatal shot was fired?”

“The Godbolds are strange, but likeable enough. The book business seems to suit them, being studious, academic types. I would be surprised if any of them knew how to hold a handgun. They were petrified when I first questioned them - concerned that the killer was still at large in the building. They claim that when the shot was fired, all three of them were in the back room of their office. Chester Godbold was prevailed upon to go out onto the stairwell and ascertain what had caused the explosion. And when he stepped outside the door, he saw the alleged gunman heading up the stairs. He called for help and was joined shortly afterwards by both his brothers and the concierge. When I questioned him later, he was unable to provide any details beyond the short description of the man you will have read in the newspaper.

“According to his account, James Mount then took charge of the proceedings. He told the Godbolds to stay where they were on the second floor while he ran down to the floor below. Having done so, he discovered Flanagan’s body and realised that the porcelain dealer had been shot. As he could see no sign of a gun, he guessed that the shooter must still be in the building and searched the back room of Flanagan’s office and then did a thorough search of the ground floor. But assuming my earlier theory to be correct, I imagine our killer had by then already left the building. Mount returned once more to the Godbolds and encouraged them to follow him down to the ground floor, where he felt they would all be safer. When they had assembled in the entrance lobby, they were concerned to hear that the lift had suddenly started to operate. The Godbolds were told to lock themselves in one of the washrooms, while Mount ran to his office and retrieved his old service revolver from a desk drawer. He was prepared for an encounter with the gunman, but when the lift had descended to the ground floor, he was relieved to see that it was occupied by Mr Cartwright and Miss Trelawney, who had left their office to find out why there was such a commotion elsewhere in the building.”

I interrupted at this point. “So, Cartwright and Trelawney were in their third floor office when the shot was fired?”

“Yes, that would appear to be the case. When I spoke to her later, Miss Trelawney said that she had heard a bang, but the sound had been some way off and had not given her much cause for concern. It was only when Cartwright emerged from the back room some minutes later, expressing some anxiety about the noise that she began to view it more seriously. Cartwright suggested that they make their way down to the ground floor to consult with the concierge. He picked up her work tray on the way out and the pair then headed for the lift in order to reach the ground floor, where they were greeted by the sight of James Mount armed with his revolver. He apologised as they emerged from the lift and explained that Flanagan had been shot and it was his firm belief that the killer was still somewhere in the building. Cartwright insisted that they all stay together on the ground floor with the exception of Miss Trelawney, who was instructed to walk to the nearest post office in order to despatch a telegram to Scotland Yard requesting immediate assistance.”

A small detail in Lestrade’s account piqued my interest. “Why did Cartwright insist on picking up Miss Trelawney’s work tray, Inspector? Did he elaborate at all?”

“Yes. He said that she had been working on some of his monthly accounts and the papers in the tray were highly confidential. He indicated that he didn’t like the idea of leaving them behind in an unlocked office and thought it was easier and quicker to pick up the tray and take it with him, rather than spend time locking doors behind him.”

“I see. And what have you found out about Cartwright and Trelawney - anything that might shed light on this curious incident?”

“Cartwright made no secret of the fact that he had been chasing Flanagan for his unpaid rent, but aside from that suggested that the two of them got along well enough. The businessman made his fortune buying and selling commercial properties and has invested a considerable amount of capital in Ravensmere Towers. He strikes me as a determined and direct fellow who usually gets what he wants. He had no clear idea about who may have wished to shoot Flanagan, but admitted that the man had not been popular with the other office workers.

“Cartwright’s secretary, Violet Trelawney, is twenty-two years of age and was taken on only recently. In fact, she has worked at Ravensmere Towers for less than a week. She was on the books of a secretarial agency before that, and was chosen by Cartwright from a shortlist of five candidates. He claims that she came with first rate credentials as a clerical worker and her references spoke highly of her character and, in particular, her integrity and reliability.”