midnight
The sense of this responsibility and the newness of his position made Jack Dudley more wakeful than he could have been under any other circumstances . To these causes , also , was due a suspicious nervousness which made him see danger where it did not exist . The rustling of a falling leaf caused him to start and glance furtively to one side , and at a soft stir of the leaves under a breath of wind , or a slight movement of the sleeping ponies , he started and grasped his rifle with closer grip . All this was natural ; but there came a moment , not far from midnight , when there remained no doubt that some person or animal was moving stealthily through the grove , near where he was standing . It will be remembered that his position was such that the trunk of the large oak acted as an impenetrable screen between him and the camp-fire , which was burning so vigorously that its rays penetrated to a greater or less degree beyond him . Thus he could see anything moving within the circle of illumination , while he was as invisible to the keenest-eyed warrior as if the night was without a ray of light . The first warning was through the sense of hearing .