As soon as he found himself alone, the detective went over and unlocked his small roll-top writing desk. When this was opened, it revealed an ebonite panel arrayed with the complicated system of knobs, coils, and valves which have now ceased to be regarded as mysteries sealed from all but the scientist. The aerial Carn had fixed for himself among the rafters in the roof; and all the essential wiring was cunningly concealed. There was need of this secrecy, for Carn, who had never served an apprenticeship to a cook while walking his beat, was forced to employ a woman from the village to look after his digestion. Village women talk—and the merest whisper that there was another radio fan in Baycombe, coming to the ears of the Tiger, would have deprived Carn of one of his most promising lines of investigation. The detective put on the headphones, plugged in, and began his systematic combing of the ether. It was not easy for Carn to use his weapon even when he was convinced of its utility. He never knew at what time the Tiger might have arranged to communicate with his agent; though he did know the discouraging fact that the Tiger always called on a different wavelength. Twice Carn had struck the tail end of a conversation, and had noted the dialling of his instrument, but the most patient listening had failed to pick up a second message; then, feeling round again, Carn had caught the same signal in a totally different range. Probably the wavelength changed according to a prearranged timetable. This, however, was Carn’s lucky day. The Tiger was using a very long wave, and Carn had reversed his usual routine and started at the top to work down the scale. He had not been probing the atmosphere for five minutes before he tuned in on a peculiar high-pitched tremulous whine which he recognised immediately for the note sent out by the Tiger’s apparatus in the gaps when no speech was coming over. And he had hardly brought the last condenser round to the exact reaction, so that the familiar note was singing in his ears at full strength, when a voice cut clean across the humming. “Don’t start to come in before it’s quite dark.” Carn stiffened. He had some idea of what was referred to. The voice continued: “Be very careful. See that there isn’t a light showing anywhere, and slow up to half speed when you’re two miles out. Change over to the electric motors at that point—— Templar stays awake at night, and his hearing’s exceptionally good.” Then another voice asked: “Can you arrange to guide us in?” “I’ll post a man on the Old House, seaward side, with a green lantern.” “Is there likely to be trouble?”