And this was not the only thing that perplexed him. Major Jefferson, who had appeared during the earlier part of the morning subdued to the point of gloominess, now wore an air of quiet satisfaction which Roger found extremely difficult to explain. Assuming that Jefferson had been extremely anxious that the police should not be the first persons to open the safe—and that was the only conclusion which Roger could draw from what had already transpired—what could have occurred in the meantime to have raised his spirits to this extent? Visions of duplicate keys and opportunities in the empty library which he himself ought to have been on hand to prevent, flashed, in rapid succession, across Roger’s mind. Yet the only possible time in which he had not been either inside the library or overlooking it were the very few minutes while he was washing his hands upstairs before lunch; and it seemed hardly probable that Jefferson would have had the nerve to utilise them in order to carry out what was in effect a minor burglary, and that with the possibility of being interrupted at any minute. It is true that he had come in very late for lunch (several minutes after Mrs. Plant, in fact); but Roger could not think this theory in the least degree probable. Yet the remarkable fact remained that the two persons who appeared to have been most concerned about the safe and its puzzling contents were now not only not in the least concerned at the prospect of its immediate official opening, but actually quietly jubilant. Or so, at any rate, it seemed to the baffled Roger. Taking it all round, Roger was not sorry that lunch was such a quiet meal. He found that he had quite a lot of thinking to do. In this respect he was no less busy when lunch was over. Alec disappeared directly after the meal, and as Barbara disappeared at the same time, Roger was glad to find one problem at least that did not seem to be beyond the scope of his deductive powers. He solved it with some satisfaction and, by looking at his watch, was able to arrive at the conclusion that he would have at least half an hour to himself before his fellow-sleuth would be ready for the trail again. Somewhat thankfully he betook himself to the friendly cedar once more, and lit his pipe preparatory to embarking upon the most concentrated spell of hard thinking he had ever faced in his life.