Perhaps I am a trifle decadent, but I cannot help believing in the splendid word; "sacrifice", for example, is surely far finer than "murder".'

'I am all in the dark,' said Phillipps. 'I cannot even imagine by what track you are moving in this labyrinth.'

'I think that before very long the whole matter will be a good deal clearer for us both, but I doubt whether you will like hearing the story.'

Dyson lit his pipe afresh and leant back, not relaxing, however, in his scrutiny of the street. After a somewhat lengthy pause, he startled Phillipps by a loud breath of relief as he rose from the chair by the window and began to pace the floor.

'It's over for the day,' he said, 'and, after all, one gets a little tired.'

Phillipps looked with inquiry into the street. The evening was darkening, and the pile of the Museum was beginning to loom indistinct before the lighting of the lamps, but the pavements were thronged and busy. The artist in chalks across the way was gathering together his materials, and blurring all the brilliance of his designs, and a little lower down there was the clang of shutters being placed in position. Phillipps could see nothing to justify Mr. Dyson's sudden abandonment of his attitude of surveillance, and grew a little irritated by all these thorny enigmas.

'Do you know, Phillipps,' said Dyson, as he strolled at ease up and down the room, 'I will tell you how I work. I go upon the theory of improbability. The theory is unknown to you? I will explain. Suppose I stand on the steps of St. Paul's and look out for a blind man lame of the left leg to pass me, it is evidently highly improbable that I shall see such a person by waiting for an hour. If I wait two hours the improbability is diminished, but is still enormous, and a watch of a whole day would give little expectation of success. But suppose I take up the same position day after day, and week after week, don't you perceive that the improbability is lessening constantly—growing smaller day after day. Don't you see that two lines which are not parallel are gradually approaching one another, drawing nearer and nearer to a point of meeting, till at last they do meet, and improbability has vanished altogether. That is how I found the black tablet: I acted on the theory of improbability. It is the only scientific principle I know of which can enable one to pick out an unknown man from amongst five million.'

'And you expect to find the interpreter of the black tablet by this method?'

'Certainly.'

'And the murderer of Sir Thomas Vivian also?'

'Yes, I expect to lay my hands on the person concerned in the death of Sir Thomas Vivian in exactly the same way.'

The rest of the evening after Phillipps had left was devoted by Dyson to sauntering in the streets, and afterwards, when the night grew late, to his literary labours, or the chase of the phrase, as he called it. The next morning the station by the window was again resumed. His meals were brought to him at the table, and he ate with his eyes on the street. With briefest intervals, snatched reluctantly from time to time, he persisted in his survey throughout the day, and only at dusk, when the shutters were put up and the 'screever' ruthlessly deleted all his labour of the day, just before the gas-lamps began to star the shadows, did he feel at liberty to quit his post. Day after day this ceaseless glance upon the street continued, till the landlady grew puzzled and aghast at such a profitless pertinacity.

But at last, one evening, when the play of lights and shadows was scarce beginning, and the clear cloudless air left all distinct and shining, there came the moment. A man of middle age, bearded and bowed, with a touch of grey about the ears, was strolling slowly along the northern pavement of Great Russell Street from the eastern end. He looked up at the Museum as he went by, and then glanced involuntarily at the art of the 'screever', and at the artist himself, who sat beside his pictures, hat in hand. The man with the beard stood still an instant, swaying slightly to and fro as if in thought, and Dyson saw his fists shut tight, and his back quivering, and the one side of his face in view twitched and grew contorted with the indescribable torment of approaching epilepsy. Dyson drew a soft hat from his pocket, and dashed the door open, taking the stair with a run.

When he reached the street, the person he had seen so agitated had turned about, and, regardless of observation, was racing wildly towards Bloomsbury Square, with his back to his former course. Mr. Dyson went up to the artist of the pavement and gave him some money, observing quietly, 'You needn't trouble to draw that thing again.'

Then he, too, turned about, and strolled idly down the street in the opposite direction to that taken by the fugitive. So the distance between Dyson and the man with the bowed head grew steadily greater.

Story of the Treasure-house

'There are many reasons why I chose your rooms for the meeting in preference to my own. Chiefly, perhaps because I thought the man would be more at his ease on neutral ground.'

'I confess, Dyson,' said Phillipps, 'that I feel both impatient and uneasy. You know my standpoint: hard matter of fact, materialism if you like, in its crudest form. But there is something about all this affair of Vivian that makes me a little restless. And how did you induce the man to come?'

'He has an exaggerated opinion of my powers. You remember what I said about the doctrine of improbability? When it does work out, it gives results which seem very amazing to a person who is not in the secret. That is eight striking, isn't it? And there goes the bell.'

They heard footsteps on the stair, and presently the door opened, and a middle-aged man, with a bowed head, bearded, and with a good deal of grizzling hair about his ears, came into the room.