When we got back to Whitehaven Mansions, Miss Lemon offered to make the tea. I went into her office and stared at this colossus of a filing-system. The office is a long one, but very thin. One wall had a hatch in it that opened on to the lounge that had served as Poirot’s consulting room. The wall opposite it housed the Colossus. This was a huge fitted cabinet, some twenty feet or so long, that spanned the entire length of the wall. How on earth were we to move it without disturbing the contents?

Miss Lemon called me from the lounge area to let me know that the tea was ready. For once, she initiated the conversation.

“You asked me whether ‘Mr Payne’ was telling the truth. I certainly did not – or, if he was, it was only in part.”

“I noticed that you were staring at him rather fixedly,” I said. “Did something in his face give him away?”

“I was not staring at him,” she replied. “I was, however, listening very closely to what he had to say, and how he said it. That was what told me he must be lying.”

“Sorry, I don’t understand.”

“That man was not Mr Payne, I’m certain of it.”

“How could you know? You said you’d never met him before.”

“I hadn’t,” she replied. “But I have spoken to him. Yesterday, on the telephone. It was not the same voice.”

“But voices can sound very different on the telephone,” I objected.

“I know.  That is why I listened very closely. It was not the same person.”

“Maybe the man on the phone was not Payne,” I suggested.

“Then why should he say he was?”

I could think of a few possible reasons, but none was very credible so I was careful not to air them to Miss Lemon. Instead I asked: “Well, what do you make of it?”

“I don’t make things of things,” she replied. “I just store and retrieve the facts. And the main fact here is this: yesterday I contacted Mr Payne to arrange an appointment to renew the lease on this apartment, with every expectation of being able to do so. He made it sound like a formality. Today, however, somebody else turned up for our appointment and turned us down flat … no pun intended,” she added, in deadpan fashion.

“‘The Mystery of Mr Payne'”, I joked. “You’d better add another card to your files.”

Miss Lemon removed her pince nez.

“Yes…” she said slowly. “I think I’d better do that. It is curious. M. Poirot always said that the seemingly insignificant, if curious, was significant. And here we have two curiosities. Someone seems to have broken into this apartment to type a letter to M. Poirot about a meeting he could not have had, and someone else impersonates the apartment’s landlord and  gives us notice to leave it.”

I considered for a moment. The letter made no sense to me, but as far as I could see Mr Payne was genuine enough, and also perfectly within his rights to give us notice to leave. I said as much, adding that we had better start looking for somewhere else to store the contents of her Colossus.

Miss Lemon walked over to the hatch that opened into her office. She seemed to be (literally) measuring things up. She frowned. Not a muscle in her moved as she stood there. I could hardly detect any sign of her breathing. Three, four minutes passed. Finally, she exhaled.

“It is a fitted piece of furniture. The only way to get it out would be to break it up and re-assemble it. We will not do that. There are thousands of cards in those drawers. They will stay where they are.”

She came back and sat down, pouring herself a cup of team as she did so.

“We have a week. One hundred and sixty-eight hours. That should easily be enough time to retrieve the sensitive material from the files, as well as decode the information required by Entwistles. We will fulfil your commission and then leave here.”

“Would it not be better to fill a few suitcases and take it all with us?” I countered.

Miss Lemon shuddered. The thought of dismantling the system she had spent years in perfecting was clearly anathema to her.

“We could, but we won’t,” Miss Lemon replied. “I am now convinced that there is something particular to this building that requires us to be here while we sort through the files. No. If we leave it here, things will start to happen, Captain Hastings.”

“Arthur,” I ventured.

“There is something going on here that we do not understand,” she continued, ignoring me. “and it could be much bigger than I had first thought. There’s work to do. I’ll draw up a timetable. We’ll both have to sleep here. I’ll take the couch.”

I was beginning to wonder who was employing who. I decided to take back control.

“I’ll take the couch, thank you,” I said, decisively. “In the meantime, as you say there is work to do. You can start by ringing the executors to tell them that they have a week to dispose of Poirot’s personal effects. But first I shall take this,” I added, walking to the wall and taking off it the Clapham Cook cheque, “in memory of my friend. Is there anything you would like to keep as a memento of Poirot?”

Before she could answer, the doorbell rang.  Miss Lemon rose.

“That will be Chief Inspector Japp. I called him earlier this morning and asked him to come round.”

“Japp!?” I exclaimed, astonished. “You summoned a top-ranking Scotland Yard official because of that letter?”

“It was not just that. I found that someone had been tampering with my drawers – ”
(I blanched) ” – and inserted something.”

I blanched further. Eyebrows raised, Miss Lemon handed me a card with the now-familiar gobbledegook on it, but in different handwriting. As I stared at it, the bell rang again.

“Not worthy of you, Captain,” Miss Lemon upbraided me as she went to answer the door.