“I think so. We’ve made inquiries. They’ve all got good histories. The commissionaire has an army pension and an excellent record. The valet and chambermaid are highly respectable-nothing whatever against them,”

“H’m. And you’ve found nothing but a packet of cigarette-papers. Handy, of course, for wrapping up a grain or so of cocaine but, in themselves, no proof of anything.”

“I thought you’d see the significance of the cigarette-papers.”

“I am not yet blind or mentally deficient.”

“But where is the dope?”

“The dope? Really, Charles! He was going to fetch the dope when friend Puncheon butted in. Haven’t you yet grasped that this is part of the Milligan crowd and that Friday is their day for distributing dope? The Milligans get it on Friday and give house-parties on Friday night and Saturday, when it goes into the hands of the actual addicts. Dian de Momerie told me so.”

“I wonder,” said Parker, “why they stick to one day? It must add to the risk.”

“It’s obviously an integral part of the system. The stuff comes into the country-say on Thursdays. That’s your part of the story. You don’t seem to have done much about that, by the way. It is taken to-somewhere or the other-that night. Next day it is called for by the Mountjoys and sent on to the Milligans, none of whom probably knows any of the others by sight. And by Saturday the whole lot is pushed out and everybody has a happy week-end.”

“That sounds plausible. It certainly explains why we found no trace of anything either in the flat or on Mountjoy’s body. Except cigarette-papers. By the way, is that right? If Mountjoy has the cigarette-papers, he ought to be the one who distributes to the addicts.”

“Not necessarily. He gets it himself in bulk-done up as Bicarbonate of Soda or what not. He divides it into small packets and parcels them out-so many to Milligan, so many to the next retailer and so forth; when, or how, I don’t know. Nor do I know how the payments are worked.”

“Glad to hear there’s something you don’t know.”

“I said I didn’t know; not that I couldn’t guess. But I won’t bother you with guesses. All the same, it’s rather surprising that Garfield & Co. left that flat alone.”

“Perhaps Garfield meant to go there afterwards, if he hadn’t got knocked out.”

“No; he’d not leave it so late. Tell me again about the flat.”

Parker patiently repeated the account of his visit and the interviews with the servants. Before he was half-way through, Wimsey had sat up in his chair and was listening with fascinated attention.

“Charles! What imbeciles we are! Of course, that’s it!”

“What’s what?”

“The Telephone Directory, of course. The man who brought the new volumes and took the old away. Since when has the Post Office taken to getting both new volumes out at once?”

“By Jove!” exclaimed Parker.

“I should think it was, by Jove. Ring up now and find out whether two new volumes were sent round to Mountjoy’s address today.”

“It’ll be a job to get hold of O.C. Directories at this time of night.”

“So it will. Wait a moment. Ring up the flats and ask if anybody else received any Directories this morning. My experience is that even Government departments do these things in batches, and don’t make a special journey to every subscriber.”

Parker acted on this suggestion. After a little trouble, he succeeded in getting into touch with three other occupants in the same block as Mountjoy’s flat. All three gave the same answer. They had received a new L-Z volume about a fortnight previously. The new A-K volume was not yet due to be issued. One man went further. His name was Barrington, and he had only recently moved in. He had inquired when the new A-K volume would be out with his new ’phone number, and had been told that it would probably be issued in October.

‘That settles it,” said Wimsey. “Our friend Mountjoy kept his secrets in the telephone directory. That great work contains advertisements, post-office regulations and names and addresses, but particularly names and addresses. May we conclude that the secret nestled among the names and addresses? I think we may.”

“It seems reasonable.”

“Very reasonable. Now, how do we set about discovering those names and addresses?”

“Bit of a job. We can probably get a description of the man who called for the books this morning-”

“And comb London’s teeming millions for him? Had we but world enough and time. Where do good telephone directories go when they die?”

“The pulping-mills, probably.”

“And the last exchange of the L-Z volume was made a fortnight ago. There’s a chance that it hasn’t been pulped yet. Get on to it, Charles. There’s more than a chance that it, too, was marked, and that the markings were transferred at each exchange from the old book to the new one.”

“Why? Mountjoy might easily have kept the old marked set by him.”

“I fancy not, or we should have either found it or heard about it from the manservant. The stranger came; the two current volumes were handed to him and he went away satisfied. As I see the plan, the whole idea would be to use the current volume, so as to rouse no suspicion, have nothing to conceal and provide a convenient mechanism for getting rid of the evidence at short notice.”

“You may be right. It’s a chance, as you say. I’ll get on to the telephone people first thing in the morning.”

The tide of luck seemed to have turned. A morning’s strenuous work revealed that the old directories had already been dispatched by the sackful to the pulping-mills, but had not, so far, been pulped. Six workers, toiling over the weekend among L-Z volumes collected from the Kensington District, brought to light the pleasing fact that nine people out of ten marked their directories in some way or another. Reports came pouring in. Wimsey sat with Parker in the latter’s office at Scotland Yard and considered the reports.

Late on Sunday night, Wimsey raised his head from a sheaf of papers.

“I think this is it, Charles.”

“What is it?” Parker was weary and his eyes blood-shot with strain, but a note of hope was in his voice.

“This one. A whole list of public-houses in Central London have been ticked off-three in the middle of the L’s, two near the end of the M’s, one in the N’s, one in the O’s, and so forth and so on, including two in the middle of the W’s. The two in the W’s are the White Stag in Wapping and the White Stoat off Oxford Street. The next W after that is the White Swan in Covent Garden. I would bet any money that in the new volume that was carried away, the White Swan was duly ticked off in its turn.”

“I’m not quite sure what you’re driving at.”

“I’m making rather a long cast, but I suggest this. When the stuff comes up to London of a Thursday, I think it is taken to which ever pub. stands next on the list in the directory. One week it will be a pub. with a name in A-say the Anchor. Next week it will be a B-the Bull & Dog, or the Brickmaker’s Arms. The week after that, it will be a C, and so on to W,X,Y,Z-if there are any. The people who have to call for their dope wander into the pub. indicated, where it is slipped to them by the head distributor and his agents, probably quite without the knowledge of the proprietor. And since it never comes twice to the same place, your pretty policemen can go and talk parrots and goats in the White Swan till they are blue in the face. They ought to have been at the Yellow Peril or the York & Lancaster.”

“That’s an idea, Peter. Let’s look at that list again.”

Wimsey handed it over.

“If you’re right, then this week was W week, and next week will be X week. That’s unlikely. Say Y week. The next Y after the last one ticked is the Yelverton Arms in Soho. Wait a minute, though. If they have been taking them in alphabetical order, why have they got right down to the end of the M’s in one case and only to WH in the other?”