Half an hour! There was not the remotest chance of intercepting him. Already, under ordinary circumstances, he would be in the outskirts of Guildford. It only remained to verify the worst. She wrote a brief message asking Mr Salt if he would kindly communicate with her immediately on his arrival, and despatched it to the agency at Guildford. If there was no reply to that request during the next half-hour she would accept the arrest as an established fact. And there being nothing apparently to do for the next half-hour, Miss Lisle, very much to the surprise of ninety-nine out of her hundred friends could they have seen her, went down on her knees in the midst of a roomful of the latest achievements of science and began to pray that a miracle might happen. * * * * * "I suppose that I may smoke?" said Salt. He was sitting handcuffed in his own motor-car, charged with murder, and formally cautioned that anything he should say might be used as evidence against him. It was scarcely a necessary warning in his case; with the exception of an equally formal protest against the arrest, he had not opened his lips until now. He and Moeletter had sat silently facing one another in the comfortably-appointed, roomy car, Salt with his face to the driver and leaning back in his easy seat with outward unconcern, the detective braced to a more alert attitude and with his knees almost touching those of his prisoner. For a mile or more--for perhaps seven or eight minutes by time, for the new driver was cautious with the yet unknown car--they had proceeded thus. Yet Salt was very far from being unconcerned as he leaned back negligently among the cushions. He was thinking keenly, and with the settled, tranquil gaze that betrayed nothing, watching alertly the miles of dreary high-road that stretched along the Hog's Back before them. He had long foreseen the possibility of arrest, and he had taken certain precautions; but to safeguard himself effectually he would have had to abandon the more important part of his work, and the risk he ran was the smaller evil of the two. But he had not anticipated this charge. Some legal jugglery with "conspiracy" had been in his mind. "I suppose that I may smoke?" Half a mile ahead a solitary wayfarer was approaching. Salt might have noted him, but there was nothing remarkable in his appearance except that pedestrians--or vehicles either, for that matter--were rare along the Hog's Back on that bitter winter afternoon. "Why, certainly, sir; in your own car, surely," replied the inspector agreeably. He was there to do his duty, and he had done it, even down to the detail of satisfying himself by search that his prisoner carried no weapon. Beyond that there was no reason to be churlish, especially as every one had to admit that there was no telling what might have happened in a week's or a month's time. "Can I help you in any way?"