He turned, but stopped abruptly when half-way across the room, standing stock still with his back to the window.

There was a faint distinct tapping as though slender fingers were beating a ghastly, distant drum.

It stopped—­it continued—­it stopped.

Then fell one little solitary rap like a drop of water falling on a metal plate, and it died away into silence.

And Sir Jonathan threw up his fine old head and laughed.

“Surely I’ve got India on the brain to-night, and as surely I want a good long holiday,” he said, as he sat down at his desk and picked up his pen.  “And I must remember to tell the gardener to clip that tree to-morrow.  How Jan will laugh when I tell him that I was absolutely scared by a branch rubbing against the window.”

For five long minutes he sat frowning down at the pen in his hand.  Three times he commenced to write, and three times he stopped; twice he lit a cigarette and let it go out, and deeper grew the lines between the brows and round the mouth, until he shivered and turned quickly in his chair.

“That felt just like a sea-fog creeping up behind; stupid to keep the window open even in spring,” he said as he picked up a log from a basket by his side and threw it deftly into the wide-open grate, leant sideways to separate two brass ornaments on a table which had jangled one against the other, and sighing turned restlessly in his chair.

“Confound those great market lorries,” he muttered, looking round the room with its cabinets and shelves filled with the strange and weird, beautiful and unsightly curios he had brought back from every corner of the globe.  “They shake the house enough to bring it down about one’s ears.”

The moon was slowly shifting as he leant back and settled himself comfortably in the high leather chair; the room was getting darker and there had fallen that intense almost palpable stillness which envelops most great cities after midnight, and against which his thoughts stood out like steel points upon a velvet curtain.

Clear and sharp as steel they shot indeed, this way and that through his mind; but hold them he could not, analyse or arrange them he could not, neither would his hand move towards the pen a few inches from the finger-tips.

“God!” he suddenly thundered, striking the arm of the chair with his fist.  “The answer is just there on the tip of my tongue—­before my very eyes—­within reach of my fingers, and yet I cannot grasp it—­ah! why! could it possibly be——­”

He rose as he spoke and crossed to a massive bookcase packed to overflowing with books, switched on a light hanging near, opened the glass door and ran his hand lovingly over the leather volumes.

Then he very gently laid his hand on his left shoulder and turned with a smile lighting up his face, which abruptly went blank in astonishment.

“Upon my word,” he said, “whatever made me think that Jan had come in and had put his hand upon my shoulder.  Old fool that I am to-night.”