“My dear Frank!”

“Yes-I know. It’s just what he might have done if he had noticed a smear which would have to be accounted for. On the other hand, he did brush up against her, and she had got a large wet patch on her sleeve. It wouldn’t be any good putting that smear on his cuff to a jury-now, would it?”

“I suppose not-unless there was other evidence in support. Was there anyone else who was marked with the paint?”

“No, there wasn’t. I think Hughes was quite thorough about that. What hadn’t occurred to him was the question as to how the paint had been carried. I think he was all out for Carroll as the murderer, and he took it for granted that the luminous mark on Porlock’s back had been made by a paint-smeared hand. Carroll’s hands were all over paint, and he had gone upstairs to wash them. Nice simple line of explanation-perfectly satisfactory to Hughes, so he never looked below what you might call the surface of the men’s handkerchiefs. I don’t think the paint could have been hidden if it had been on one of those flimsy squares of muslin that women drop about all over the place-it would have come through.”

Miss Silver coughed gently.

“My dear boy, not muslin-cambric, or linen.”

An almost colourless eyebrow jerked.

“Call them anything you like-paint would show through. But a man’s handkerchief could be carefully folded up to hide a paint-stain. Hughes just looked blank when I asked him if he’d had all the handkerchiefs spread out. He hadn’t. You expect a man to have a handkerchief-you take it for granted. At least you don’t, but Hughes did. Which gives the murderer the best part of twenty-four hours to get rid of the evidence. By the time I’d thought about a handkerchief and put Hughes on to going through the house with a toothcomb there naturally wasn’t anything left for him to find.”

Miss Silver put away her knitting and got up.

“I should like to go into the hall, but before we do so, will you tell me what results have been obtained in the way of fingerprints?”

“I think I told you about the four sets of switches. The one at the top of the stairs had been wiped clean. The one by the service door was just a mess. The one by the hearth had Masterman’s prints, and the one by the hall door Justin Leigh’s-both quite innocently accounted for. The dagger had been wiped clean-there were no prints there-” He stopped beneath a searching gaze.

“Were no other prints found?”

The eyebrow jerked again.

“What other prints were there to take? Most of these people were staying in the house. The others had been dining, moving about in the hall. Their prints would be all over the place, and they wouldn’t prove a thing.”

Miss Silver coughed, picked up Justin Leigh’s plan, and led the way into the hall.

It was empty. The electric candles shed a soft light upon the stone flags and the two long Persian runners which crossed them. But Miss Silver was not looking at the floor. She walked over to the hearth and stood there, her eyes lifted to the trophy of arms above the stone mantelshelf. Hanging there on the broad chimney-breast, it had the air of some military decoration pinned to a rough grey coat, for the chimney-breast like the ledge was of stone, breaking the panelled wall. There were old flintlocks, four cumbersome pistols, and a ring of daggers. The bottom dagger was missing. Miss Silver stood looking at the place where it had been.

After a little while she turned round and looked in the direction of the stairs. Then she turned her head, glanced towards the switches on the left-hand side of the hearth, and back again at the staircase. At the sound of approaching voices she went back into the study. When she had seated herself and taken up her knitting again she enquired,

“How tall are you, Frank?”

He looked surprised.

“Five-foot-eleven.”

“Mr. Masterman would be a little taller?”

He said, “Yes. Oakley and Masterman are both taller-about six foot. I should give Justin Leigh another inch. Moira Lane must be all of five-foot-nine-Dorinda Brown not quite so tall. Mrs. Oakley is about your height. Tote not more than five-foot-seven.”

She said, “I was extremely pleased to observe that there was dust upon the mantelshelf-quite a considerable amount. It seemed almost too much to hope for, but the hall does not really look as if it had been dusted.”

Frank Abbott laughed.

“I don’t suppose it has. Pearson had the sense to leave everything until we came, and I told him to go on leaving it until I said-well, I’m afraid I quite forgot to say.”

Miss Silver smiled.

“A truly fortunate circumstance.”

He was sitting astride one of the upright chairs with his arms folded on the back…

“Now, what are you getting at?”

She was knitting rapidly.

“I hope that it may be possible to recover fingerprints which may prove of great importance. I should like you to ring up and ask to have someone sent out at once. Will you do so?”

He looked at her sharply.

“Blind?”

She smiled. Miss Silver’s smile had an extraordinary charm. It had before now captured hearts and converted the sceptic. Frank Abbott’s heart had been captured long ago. A young man not much given to enthusiasms, he undoubtedly had one for his “revered preceptress.” He had also a very complete confidence in her judgment. When, therefore, she said primly, “I do not think there is any time to be lost,” he got up, went over to the table, and picked up the telephone receiver.

When the ensuing short conversation had been closed by a definitive click he came back to his place and said,

“All right, ma’am. Do I get anything explained to me, or do I just wait for the explosion?”

This time she did not smile. She looked across the busy needles and the pale pink wool and said,

“I shall be very happy to explain. But before I do so, perhaps you will go into the hall and measure the distance from the ground to where the handle of the missing dagger would have been.”

“Oh-so that’s it? All right.”

He went out and came back again.

“Six foot or thereabouts. I take it fractions don’t matter.”

“No. I believe you see my point. The stone ledge which crosses the chimney breast and serves as a mantelshelf is, I should say, twelve to fourteen inches lower. It is perhaps fourteen inches deep. It has occurred to me that scarcely anyone would reach across such a ledge to remove an object hanging just above it without putting a hand upon the ledge. Of course-as you are about to say-anyone staying in the house might have rested a hand upon that shelf without having any connection with the murder. But if the prints of a suspect were found, their position and direction might prove valuable corroborative evidence.”

He nodded.

“Have you got anything else up your sleeve?”

The smile came out again.

“I think so. All the suspects are known to have been present in the hall at the time that Gregory Porlock was stabbed, with the exception of Mr. Tote, who may have been in the drawing-room or waiting behind the service-door, and Mr. Carroll, who had gone upstairs to wash and was found to be on the third step from the top of the stairs when the lights came on after the murder. If we are accepting it as an axiom-and I think we must-that it was the murderer who had turned out the lights, Mr. Carroll, if it was he, could only have done so by using the switches at the top of the stairs. And the probabilities are that Mr. Tote, if it was he, would have used the switches at the back of the hall by the service door. These probabilities appear to be so strong as almost to constitute a certainty. For everybody else there was only one set of switches which was both accessible and, owing to the shifting of the group round the fire, not too much exposed to observation. I refer to the switches on the left of the hearth. Now, my dear Frank, pray consider. Leaving Mr. Carroll and Mr. Tote on one side for the moment, let us suppose that the murderer is one of that group round the fire. He has his plan all ready. He has put his mark on Gregory Porlock’s back so as to make sure of finding a vital place in the dark. He turns out the lights. Now remember that Mr. Porlock, who had gone over in the direction of the staircase, had already turned and was coming back. That is to say, he was facing the murderer, and the bright spot of luminous paint on his back was therefore not visible. What would the murderer do? I think he would cross the hall as quickly as he could with a hand stretched out in front of him till he came up against the staircase. This would bring him behind his victim, and at no great distance. The luminous patch would be right in front of him as he turned, and he would only have to step forward and strike.”