“That very man!” affirmed the Professor solemnly. “Good Lord! What does all this mean?” Blick suddenly dropped on his knees by the dead man’s side and abruptly plunged a hand into an inner pocket of the clothing—into a second—a third. Just as suddenly he produced a letter-case, and from it drew out a wad of bank-notes and two papers. He dropped the notes unconcernedly on the stones, and hastily unfolded the papers; a second later he thrust these into the Professor’s hand. “That’s what it means!” he said quietly. “There’s Spindler’s formula, and there’s your opinion about it. And—this is the chap who killed Guy Markenmore!” Then he looked round at the three men. The Professor was staring blankly at the papers just handed to him; Mr. Fransemmery was staring at the Professor; Harborough, anxious and puzzled, was looking doubtfully at the dead man. It was he who spoke first, turning to the detective. “You think he—that he killed Guy Markenmore in order to get possession of—those?” he asked, in a low voice. Blick rose from his knees. “What else?” he said calmly. “I see the whole thing now! Sir Thomas, there, and I already know something of it, but up to a few minutes ago I didn’t suspect this man. But, as I say, now I see it—clearly enough. This man, whom I met a few nights ago at the Sceptre, posing as Crawley, a holidaymaker, taking a walking tour round this country, is in reality Carter, an assistant of Sir Thomas’s at his laboratory at Cambridge. It was he to whom Sir Thomas entrusted a sealed packet for direct conveyance to Guy Markenmore in London; he, Carter, was passing through London on his way here for his holiday. Now, although Carter did not know the nature of the precise contents of that packet, he had learnt from Sir Thomas that they were of immense scientific and monetary value. He was charged to put the packet into Guy Markenmore’s own hands. He did so. Later that day Guy Markenmore travelled down here. So did Carter. Probably they met on the train; probably they travelled in company. But, at any rate, Sir Thomas and I have just found out that Guy Markenmore and Carter were together on these downs late that night, talking confidentially. Now from what I’ve learned about him, Guy Markenmore was a talkative, free-and-easy sort of a man, open and candid; probably, knowing that Carter was Sir Thomas’s assistant, Guy took Carter into his confidence about the secret. And Sir Thomas and I have just ascertained that Guy told Carter that he would be at or about Markenmore Hollow at a very early hour next morning. What does Carter do? He forms the plan of hanging about all night—a warm night, mind!—waylaying Guy early in the morning and murdering him for the secret and for the money which was to be put together for it that night by Guy, Lansbury, and Baron von Eckhardstein. And—he carries all this into execution. What does he do, then? Goes quietly away amongst these hills and woods on his