When they were in the lift, Mr Cartwright had chatted to her about a musical performance he had seen the previous evening and seemed far more lively than usual. On reaching the office, he had unlocked the door to their rooms and she had taken a seat at her desk. She then waited for Mr Cartwright to go through to his room and return a short while later with the wooden tray which contained her work for the day. He gave instructions that he was not to be disturbed under any circumstances and had retreated into his room once more, closing the door behind him. This was the pattern that had been followed every day that Violet Trelawney had worked at Ravensmere Towers. Very occasionally, Mr Cartwright might emerge from his room with some additional requests, but, on the whole, the secretary was required to work diligently through her allotted work until one-thirty, when Mr Cartwright would come out from his room to announce the time and allow the young woman to go home for the day.

At this point, Holmes cut in. “Miss Trelawney, I think you have forgotten one small detail of the events yesterday. I understand that you placed an apple in your desk drawer?”

Miss Trelawney flushed. “Yes, I’m sorry, Mr Holmes. I had forgotten to mention that. When Mr Cartwright was in his office, I took the Worcester Pearmain from my bag and placed it in the drawer. When the police allowed me to return to the room in the afternoon, I found it had gone.”

Archibald Cartwright scoffed loudly on hearing this and glowered at Holmes. “I might have thought that a consulting detective would have other, more pressing, matters to attend to, beyond a concern for missing fruit,” he announced drily.

Holmes dealt with the challenge head on. “Sir, the absence of the apple lies at the very heart of this mystery as we will discover.” Once more he turned his attention to Miss Trelawney: “Perhaps you could explain what happened when you heard the shot at around eleven o’clock?”

“Yes. I heard the noise, but did not realise it was a gunshot until later. From where I sat, it was not particularly loud and I was a little surprised when Mr Cartwright came out of his room a good three or four minutes later, expressing some concern about it. He picked up my work tray and asked me to follow him to the lift, which we took to get to the ground floor where the others were then assembled. I was very upset to hear that Mr Flanagan had been shot.”

“Indeed. And was there anything else that struck you as odd that morning?”

“Only one thing, Mr Holmes. I imagine it might be the drabness of the room in which I work, particularly with the absence of any windows or natural light, but I did at one point imagine that the walls were closing in on me. It made me feel quite giddy in fact.”

Holmes smiled at her. “That is most enlightening, thank you. And a final question for you, Inspector Lestrade.”

“Yes, Mr Holmes?”

“I understand you conducted a thorough search of the building when you first heard that the gunman had been seen ascending the stairs from the second floor?”

“That is correct. We looked in every room and checked every conceivable hiding place. The killer had clearly fled the building.”

“And what if the killer had been one of the people already in the building - one of those now stood before us?”

There was considerable excitement at this point but Lestrade sought to quash the matter. “Mr Holmes, the killer cannot have been any of these good people. Each has a strong alibi and we could find no handgun on any of them. We searched every desk, drawer, cabinet and cupboard and found nothing to incriminate anybody.”

“Ah, so you searched every room for the murder weapon?”

Lestrade looked confused. “Well, we conducted a detailed search of the ground floor and the first three upper floors, Mr Holmes. I admit that we undertook only a cursory exploration of floors four and five, principally to look for the killer - if we’d found him, we would have found the gun. There seemed little point searching any furniture on those floors as none of our suspects occupied the rooms.”

“I see,” said Holmes. “You will forgive me for pressing the point, but I just wanted to be clear. Now that you have given me that one final piece of the jigsaw, I am certain that I know how the murder was committed yesterday and who our killer is.”

It was the Godbold brothers who were most voluble on hearing this and Violet Trelawney looked flabbergasted. Holmes then announced what was to be done. “If PC Clarke and Mr Mount are content to stand guard, I suggest that Inspector Lestrade and Miss Trelawney accompany Dr Watson and I in the lift to the third floor. I will then explain the sequence of events yesterday morning.”

At this, Archibald Cartwright flared up and rounded on Holmes. “Sir, I refuse to be held captive in my own building! If you are suggesting that one of us committed this heinous crime, I insist that you provide us with the evidence for your assertions. Until such a time, I will not let you curtail my movements.”

Holmes was unperturbed by Cartwright’s outburst and extended him an invitation. “My dear fellow - I will be pleased to provide you with the proof you suggest. Perhaps you can stand in for Miss Trelawney on our short excursion. In fact, that would be a much better plan given that it was you that shot and killed Mr Edward J Flanagan.”

There was not a little surprise at Holmes’ announcement. Frederick Godbold, the youngest of the three brothers, swayed as if he was about to faint. Violet Trelawney looked close to tears and even Inspector Lestrade appeared to be astonished by the revelation. Of those present, it was Archibald Cartwright who remained the most composed of the group.

“Sir, you seem to be forgetting that I have a solid alibi for where I was at the time of the shooting. Miss Trelawney has confirmed that we arrived at the office together. Having given her a few tasks for completion, I withdrew to the back room. I only emerged from the room after I had heard the shot on the first floor. I think you will agree that if I had tried to leave the office by passing through Miss Trelawney’s room, my secretary would, without doubt, have seen me.”

Holmes reflected on Cartwright’s words for a couple of seconds and then responded. “Yes, Mr Cartwright. There is a perfect logic to what you have said. And yet, it does not provide you with an alibi at all. I suggest that our party of four takes that trip to the third floor. All will become clearer as we travel up through the building.”

Leaving the others in the lobby, Holmes and I escorted Lestrade and Cartwright towards the lift. We were safely ensconced within the elevator when Holmes began his narrative. “Gentlemen, Violet Trelawney was employed by Archibald Cartwright less than a week ago. Her excellent references spoke for her. He took her on because she was both hardworking and honest - not because he needed a secretary, but because she would provide him with an almost perfect alibi.”

I could see Cartwright grinding his teeth, his jaw set hard and his eyes fixed firmly on the floor of the lift. Holmes operated a lever for the third floor and with a sudden jolt the mechanism was propelled into action, accompanied by a loud hiss and the noisy whirring of the machinery above and below us. I felt somewhat unnerved and momentarily dizzy as we began to ascend upwards.

Holmes raised his voice above the level of the clatter. “Miss Trelawney stated that when she emerged from the ladies washroom on the fateful morning, Mr Cartwright was waiting for her at the entrance to this lift. It is my contention that this was no coincidence. He planned it that way. It was essential that he take control of the lift and ensure that it was not the lever to their third floor office that was engaged, but the lever to the fourth floor instead. Miss Trelawney described him as being more lively than usual. His idle banter provided a cover for the deception he was perpetrating. The intention was to convince her that she was heading towards the third floor office as she had done every day since entering his employment.”