He knew that Manderson’s room was the first on the right hand when the bedroom floor was reached, and he went to it at once. He tried the latch and the lock, which worked normally, and examined the wards of the key. Then he turned to the room.

It was a small apartment, strangely bare. The plutocrat’s toilet appointments were of the simplest. All remained just as it had been on the morning of the ghastly discovery in the grounds. The sheets and blankets of the unmade bed lay tumbled over a narrow wooden bedstead, and the sun shone brightly through the window upon them. It gleamed, too, upon the gold parts of the delicate work of dentistry that lay in water in a shallow bowl of glass placed on a small, plain table by the bedside. On this also stood a wrought-iron candlestick. Some clothing lay untidily over one of the two rush-bottomed chairs. Various objects on the top of a chest of drawers, which had been used as a dressing-table, lay in such disorder as a hurried man might make. Trent looked them over with a questing eye. He noted also that the occupant of the room had neither washed nor shaved. With his finger he turned over the dental plate in the bowl, and frowned again at its incomprehensible presence.

The emptiness and disarray of the little room, flooded by the sunbeams, were producing in Trent a sense of gruesomeness. His fancy called up a picture of a haggard man dressing himself in careful silence by the first light of dawn, glancing constantly at the inner door behind which his wife slept, his eyes full of some terror.

Trent shivered, and to fix his mind again on actualities, opened two tall cupboards in the wall on either side of the bed. They contained clothing, a large choice of which had evidently been one of the very few conditions of comfort for the man who had slept there.

In the matter of shoes, also, Manderson had allowed himself the advantage of wealth. An extraordinary number of these, treed and carefully kept, was ranged on two long low shelves against the wall. No boots were among them. Trent, himself an amateur of good shoe-leather, now turned to these, and glanced over the collection with an appreciative eye. It was to be seen that Manderson had been inclined to pride himself on a rather small and well-formed foot. The shoes were of a distinctive shape, narrow and round-toed, beautifully made; all were evidently from the same last.

Suddenly his eyes narrowed themselves over a pair of patent-leather shoes on the upper shelf.

These were the shoes of which the inspector had already described the position to him; the shoes worn by Manderson the night before his death. They were a well-worn pair, he saw at once; he saw, too, that they had been very recently polished. Something about the uppers of these shoes had seized his attention. He bent lower and frowned over them, comparing what he saw with the appearance of the neighbouring shoes. Then he took them up and examined the line of junction of the uppers with the soles.

As he did this, Trent began unconsciously to whistle faintly, and with great precision, an air which Inspector Murch, if he had been present, would have recognized.

Most men who have the habit of self-control have also some involuntary trick which tells those who know them that they are suppressing excitement. The inspector had noted that when Trent had picked up a strong scent he whistled faintly a certain melodious passage; though the inspector could not have told you that it was in fact the opening movement of Mendelssohn’s Lied ohne Worter in A Major.

He turned the shoes over, made some measurements with a marked tape, and looked minutely at the bottoms. On each, in the angle between the heel and the instep, he detected a faint trace of red gravel.