"Mr. Ewart was to take no notice whatever of anything Mr. Garnesk said in his letter about Mr. Hilderman. He was on no account to trust Mr. Hilderman, but to be very careful not to let him see he was suspected. The gentlemen were always to wear their glasses whenever they were in sight of the hut above--Glas.--above Mr. Hilderman's house." "Whew!" Dennis whistled. "But why didn't he----? Oh, I see. He was afraid the letter might fall into Hilderman's hands." "I wonder where Ron can have got to?" Myra mused wistfully. "We're very much obliged to you for all the trouble you have taken, Mr. McKenzie," said Dennis. "You've done very well indeed." "Oh, Mr. Garnesk also said that Miss McLeod was to put on her glasses by the red light." "Yes; that's important," Dennis agreed. "We'll go up to the house now, shall we, Miss McLeod?" "Yes," said Myra, "and Mr. McKenzie must come and have a meal and a rest, as I'm sure he needs both after his journey. I'll send Angus to look after the boatman." So the three strolled up to the lodge. "By the way," said Dennis, "of course it's all right, and you've carried out your instructions to the letter, but how can you be sure this is Miss McLeod, and how do you know I'm not Hilderman?" "Mr. Garnesk described everybody I should be likely to meet," McKenzie replied, "including Mr. Hilderman and Mr. Fuller. I know you are Mr. Ewart's friend because you have a small white scar above your left eyebrow. So, being with you, and wearing a shade and an Indian bangle, I thought I was safe in concluding the lady was Miss McLeod." "Garnesk doesn't seem to miss much!" Dennis laughed. "He made me repeat his descriptions about twenty times," said McKenzie, "so I felt pretty sure of myself." When they got up to the lodge, and the messenger's requirements had been administered to, Dennis unpacked the parcel. The spectacles proved to be something like motor goggles; they fitted closely over the nose and forehead, and entirely excluded all light except that which could be seen through the glass. The only curious thing about them was the glass itself. Instead of being white, or even blue, it was red, and the surface was scratched diagonally in minute parallel lines. Myra and Dennis hurried upstairs, and lighted the lamp in the dark-room. When the girl came down again she declared that she could see beautifully. Everything was red, of course, but she could see quite distinctly. "Have you any idea why these glasses are ruled in lines like this?" Dennis asked McKenzie. "I couldn't say for certain, sir," the youth replied. "But I should think it was because Mr. Garnesk thought the glasses would be so near the eye as to be ineffective. In photography, for instance, you can't print either bromide or printing-out paper in a red light. But if you coat a red glass with emulsion, and make an exposure on it, you can print the negative in the usual way. I don't know why it is."