The next afternoon the study of the vicar of Gylston presented a strange appearance.

Seated at Mr. Crayne's writing-table was Malcolm Sage, a small attachÉ-case at his side, whilst before him were several piles of sealed packets. Grouped about the room were Inspector Murdy, Robert Freynes, Mr. Gray, and the vicar.

All had their eyes fixed upon Malcolm Sage; but with varying expressions. Those of the schoolmaster were frankly cynical. The inspector and Freynes looked as if they expected to see produced from the attachÉ-case a guinea-pig or a white rabbit, pink-eyed and kicking; whilst the vicar had obviously not yet recovered from his surprise at discovering that the stranger, who had shown such a remarkable knowledge of monumental brasses and Norman architecture, was none other than the famous investigator about whom he had read so much in the newspapers.

With quiet deliberation Malcolm Sage opened the attachÉ-case and produced a spirit lamp, which he lighted. He then placed a metal plate upon a rest above the flame. On this he imposed a thicker plate of a similar metal that looked like steel; but it had a handle across the middle, rather resembling that of a tool used by plasterers.

He then glanced up, apparently unconscious of the almost feverish interest with which his every movement was being watched.

"I should like Miss Crayne to be present," he said.

As he spoke the door opened and the curate entered, his dark, handsome face lined and careworn. It was obvious that he had suffered. He bowed, and then looked about him, without any suggestion of embarrassment.

Malcolm Sage rose and held out his hand; Freynes followed suit.

"Ask Miss Muriel to come here," said the vicar to the maid as she was closing the door.

The curate took the seat that Malcolm Sage indicated beside him.
Silently the six men waited.

A few minutes later Miss Crayne entered, pale but self-possessed. She closed the door behind her. Suddenly she caught sight of the curate. Her eyes widened, and her paleness seemed to become accentuated. A moment later it was followed by a crimson flush. She hesitated, her hands clenched at her side, then with a manifest effort she appeared to control herself and, with a slight smile and inclination of her head, took the chair the schoolmaster moved towards her. Instinctively she turned her eyes toward Malcolm Sage.

"Inspector Murdy," he said, without raising his eyes, "will you please open two of those packets?" He indicated the pile upon his left. "I should explain," he continued, "that each of these contains one of the most recent of the series of letters with which we are concerned. Each was sealed up by Mr. Crayne immediately it reached him, in accordance with Inspector Murdy's request. Therefore, only the writer, the recipient and the vicar have had access to these letters."

Malcolm Sage turned his eyes interrogatingly upon Mr. Crayne, who bowed.

Meanwhile the inspector had cut open the two top envelopes, unfolded the sheets of paper they contained, and handed them to Malcolm Sage.

All eyes were fixed upon his long, shapely fingers as he smoothed out one of the sheets of paper upon the vicar's blotting-pad. Then, lifting the steel plate by the handle, he placed it upon the upturned sheet of paper.

The tension was almost unendurable. The heavy breathing of Inspector Murdy seemed like the blowing of a grampus. Mr. Gray glanced across at him irritably. The vicar coughed slightly, then looked startled that he had made so much noise.

Everyone bent forward, eagerly expecting something; yet without quite knowing what. Malcolm Sage lifted the metal plate from the letter. There in the centre of the page, in bluish-coloured letters, which had not been there when the paper was smoothed out upon the blotting-pad, appeared the words:——

Malcolm Sage,
August 12th, 1919.
No. 138.

For some moments they all gazed at the paper as if the mysterious blue letters exercised upon them some hypnotic influence.

"Secret ink!"

It was Robert Freynes who spoke. Accustomed as he was to dramatic moments, he was conscious of a strange dryness at the back of his throat, and a consequent huskiness of voice.

His remark seemed to break the spell. Instinctively everyone turned to him. The significance of the bluish-coloured characters was slowly dawning upon the inspector; but the others still seemed puzzled to account for their presence.

Immediately he had lifted the plate from the letter, Malcolm Sage had drawn a sheet of plain sermon paper from the rack before him. This he subjected to the same treatment as the letter. When a few seconds later he exposed it, there in the centre appeared the same words:——

Malcolm Sage,
August 12th, 1919.

but on this sheet the number was 203.

Then the true significance of the two sheets of paper seemed to dawn upon the onlookers.

Suddenly there was a scream, and Muriel Crayne fell forward on to the floor.

"Oh! father, father, forgive me!" she cried, and the next moment she was beating the floor with her hands in violent hysterics.