“Any confirmation of that?”

“One of his men remembers him there but can’t say exactly when or for how long. He was talking to Sir Herbert Carrados.”

“To Carrados? I see. How did Dimitri shape when you saw him?”

“Well,” said Fox slowly, “he’s a pretty cool customer, isn’t he? Foreign, half-Italian, half-Greek, but that’s hardly noticeable in his speech. He answered everything very smoothly and kept saying it was all very regrettable.”

“I trust he’ll find it even more so,” said Alleyn and returned to the notebook.

“The rest,” said Fox, “left after Lord Robert and as far as we can make out, some time after. There are only three names and I don’t fancy they’ll amount to much, but I thought we’d better have them.”

“When did the Carrados party go? Last of all, of course?”

“Yes. Sir Herbert and Lady Carrados were at the head of the stairs on the ballroom landing saying good-bye most of this time, but Sir Herbert must have come down to the buffet if it’s right that Dimitri talked to him there. I’ve left Sir Herbert to you, Mr Alleyn. From what I hear of him he’ll need handling.”

“Extraordinarily kind of you,” said Alleyn grimly. “Is there any exit from the buffet other than the one into the hall?”

“Yes, there is. A door that gives on to the back stairs down to the basement.”

“So it’s conceivable that Dimitri might have gone out into the street that way?”

“Yes,” agreed Fox. “It’s possible, all right. And come back.”

“He would have been away at least forty minutes,” said Aileyn, “if he’s our man. If, if, if! Would he be able to get hold of a topper? The murderer wore one. What would he say to Bunchy to persuade him to give him a lift? ‘I want to talk to you about blackmail?’ Well — that might work.”

“For all we know,” said Fox, “it may not have been any of the guests or Dimitri.”

“True enough. For all we know. All the same, Fox, it looks as if it was. It’s not easy to fit an outsider into what facts we’ve got. Try. An unknown in full evening dress wearing an overcoat and a top-hat stands outside Marsdon House waiting for Lord Robert to come out and on the off-chance of getting a lift. He doesn’t know when Lord Robert will leave, so he has to hang about for three hours. He doesn’t know if he’ll get a chance to speak to Lord Robert, whether Lord Robert will leave in a party or alone, in a private car or a taxi. He doesn’t know a heavy mist is going to crawl over London at one o’clock.”

“He might have just happened to come up,” said Fox and added immediately: “All right, all right, sir. I won’t press it. We’ve got plenty to go on from inside and it’s a bit far-fetched, I will allow.”

“The whole thing’s too damn far-fetched, in my opinion,” said Alleyn. “We’re up against a murder that was very nearly unpremeditated.”

“How do you make that out?”

“Why, Fox, for the reasons we’ve just ticked off. Lord Robert’s movements could not be anticipated. I have just learned that he had intended to leave much earlier with his sister, Lady Mildred Potter, and Miss Troy.”

“Miss Agatha Troy?”

“Yes, Fox.” Alleyn turned aside and looked out of the window. “She’s a friend of the family. I’ve spoken to her. She’s here.”

“Fancy that, now,” said Fox comfortably.

“I think,” continued Alleyn after a pause, “that when the murderer went out from the lighted house into that unwholesome air he perhaps knew that Bunchy — Lord Robert — was returning alone. He may have seen him alone in the hall. That’s why your little list is important. If the man was Dimitri he went out with the deliberate intention of accomplishing his crime. If it was one of the guests he may have made up his mind only when he caught a glimpse of Bunchy standing alone in the mist, waiting for a taxi. He may have meant to threaten, or reason, or plead. He may have found Bunchy obdurate, and on an impulse killed him.”

“How do you reckon he brought it off? With what?”

“Back to the jurists’ maxim,” said Alleyn with a slight smile: “Quis, quid, ubi, quibus auxilus, cur, quomodo, quando?”

“I never can remember it that way,” said Fox, “knowing no Latin. But I’ve got old Gross’s rhyme all right:

“Yes,” said Alleyn. “We’ve got quid, quomodo and ubi, but we’re not so sure of quibus auxiliis. Dr Curtis says the abrasion on the temple is two and a half inches long and one-twelfth of an inch across. The blow, he thinks, was not necessarily very heavy, but sharp and extremely accurate. What sort of implement does that suggest to you, Fox?”

“I’ve been thinking that—”

The desk telephone rang. Alleyn answered it.

“Hullo?”

“Mr Alleyn? The Yard here. Sir Daniel Davidson has rung up and says he may have something to tell you. He’ll be in all day.”

“Where is he?”

“In his rooms, number fifty St. Luke’s Chambers, Harley Street.”

“Say I’ll call at two o’clock. Thank him.” Alleyn put the receiver down.

“Davidson,” he said, “thinks he may have something to relate. I bet he had a heart-to-heart talk with himself before he decided to ring up.”

“Why?” asked Fox. “Do you mean he feels shaky?”

“I mean he’s a fashionable doctor and they don’t care for the kind of publicity you get from criminal investigations. If he’s a clever fellow, and I imagine he must be to have got where he is, he’s realized he was one of the last people to see Lord Robert. He’s decided to come to us before we go to him. According to your notes, Fox, Sir Daniel was the first of the last three people to leave before Lord Robert. The other two were a tight young gentleman and a female secretary. Sir Daniel would have seen Lord Robert was alone and about to leave. He could have waited outside in the mist and asked for a lift in the taxi as easily as anybody. I wonder if he realizes that.”

“No motive,” said Fox.

“None, I should imagine. I mustn’t get fantastic, must I? Damn young Potter, why doesn’t he come?”

“Have you finished here, sir?”

“Yes. I got here at five o’clock this morning, broke the news to Lady Mildred, and settled down to Lord Robert’s dressing-room, bedroom and this study. There’s nothing at all to be found except his notes and the will. From seven until ten I looked in their garden, the neighbouring gardens and up and down the Embankment for a cloak and a soft hat. With no success. I’ve got a squad of men at it now.”

“He may not have got rid of them.”

“No. He may have been afraid of leaving some trace of himself. If that’s the case he’ll want to destroy or lose them. It was low tide at three o’clock this morning. To drop them in the driver he’d have to get to a bridge. What sort of house is Dimitri’s?”

“It’s a small two-roomed flat in the Cromwell Road. He keeps a servant. French, I should say.”

“We’ll go round there at noon when he’s due at the Yard, and see if we can find anything. You’ve seen the flat. Where’s his telephone?”

“On the landing.”

“Right. You’d better ring from the nearest call-box as soon as I’ve gone in. Keep the servant on the telephone as long as possible. You can put a string of questions about the time Dimitri got in, ask for the names of some of the men, anything. I’ll have a quick look round for a possible spot to hide a largish parcel. We must get the dust-bins watched, though he’s not likely to risk that. Blast this nephew. Fox, go and do your stuff with the maids. Don’t disturb Lady Mildred, but ask for Mr Donald’s telephone number. It’s written on a memorandum in her room, but they may have it, too.”

Fox went out and returned in a few minutes.

“Sloane 8405.”

Alleyn reached for the telephone and dialled a number. “Chief Detective-Inspector Alleyn, Scotland Yard. I want you to trace Sloane 8405 at once, please. I’ll hang on.”