Once there came a startling interruption, in the sliding of some gravel down the gully. Pistol in hand, Dick whirled, and for ten monstrously elongated seconds listened to the irregular beats of his heart as he waited. Satisfied at length that it was only a chance avalanche in miniature, he got down on his hands and knees above the plainest of the vestigia. There was the secret, if he only could read it. Had Haynes solved it and met his death at the moment of success? For perhaps two or three minutes the young doctor remained in his crouched posture, his mind immersed in speculation. Then he rose, facing the sea, and as he stood and looked down there came to him a sudden glow of illumination. “By the heavens! I’ve got it!” he cried. He started forward to the next mark. As he advanced, something sang in the air behind him. He knew it was some swiftly flying thing; knew in the same agonised moment that the doom of Haynes and Serdholm was upon him: tried to turn and face his death—and then there was a dreadful, grinding shock, a flame with jagged edges tore through his brain, and he fell forward into darkness. CHAPTER FIFTEEN THE PROFESSOR ACTS PROMPTITUDE was one of Professor Ravenden’s many virtues. Only one thing could make him forget the obligation of an engagement; that was his dominant ardour for the hunt. In time this had become an instinct. So it is not strange that, on leaving Third House to keep his rendezvous with Dick Colton, he should have absentmindedly hung his heavy poison-jar for specimens around his neck, and taken up his butterfly net, while entirely forgetting his revolver. As chance would have it, there rose about the same hour as Professor Ravenden a delicate little butterfly with wings like the azure glory of the mid-June heavens. It was taking the air on a leaf of scrub-oak, while waiting for the sun to come out, when the entomologist came striding over the knolls, and brushed against the shrub. Up fluttered the beautiful insect, and the blue of its wings caught the eager eye of Professor Ravenden. It was of the same species which once before had lured him from the greater pursuit. “_Lycama pseudargiolus_,” he muttered, as he hastily affixed his collapsible net. “From its brightness, it should be a fall specimen, and undoubtedly shows the variations on the lower wing which I am studying. Wait one moment, my friend, and I shall welcome you to the hospitality of my cyanide jar.”