Night, with the sinister, brooding peace of the desert, enwrapped the land, and the inmates of the old Karoo farm had long been at rest; but it was an hour when strange tree-creatures cry with the voices of human beings, and stealthy velvet-footed things prowl through places forbidden by day, and not all who rested at Blue Aloes were sleeping.Christine Chaine, wakeful and nervous, listening to the night sounds, found them far more distracting than any the day could produce. Above the breathing of the three children sleeping near her in the big room, the buzz of a moth-beetle against the ceiling, and the far-off howling of jackals, she could hear something out in the garden sighing with faint, whistling sighs. More disquieting still was a gentle, intermittent tapping on the closed and heavily barred shutters, inside which the windows stood open, inviting coolness. She had heard that tapping every one of the three nights since she came to the farm.The window stood to the right of her bed, and, by stretching an arm, she could have unbolted the shutters and looked out, but she would have died rather than do it. Not that she was a coward. But there was some sinister quality in the night noises of this old Karoo farm that weighed on her courage and paralyzed her senses. So, instead of stirring, she lay very still in the darkness, the loud, uncertain beats of her heart adding themselves to all the other disconcerting sounds.Mrs. van Cannan had laughed her lazy, liquid laugh when Christine spoke, the first morning after her arrival, of the tapping."It was probably a stray ostrich pecking on your shutters," said the mistress of Blue Aloes. "You are strange to the Karoo, my dear. When you have been here a month, you'll take no notice of night noises."There was possibly truth in the prophecy, but Christine doubted it. There were also moments when she doubted being able to last a week out at the farm, to say nothing of a month. That was only in the night watches, however; by day, she found it hard to imagine any circumstances so unpleasant as to induce her to leave the three little van Cannan children, who, even in so short a time, had managed to twine their fingers and their mops of bronze hair round her affections.The tapping began again, soft and insistent. Christine knew it was not a branch, for she had taken the trouble to ascertain; and that a stray ostrich should choose her window to peck at for three nights running seemed fantastic. Irrelatively, one of the children murmured drowsily in sleep, and the little human sound braced the girl's nerves. The sense of loneliness left her, giving place to courageous resolution. She forgot everything save that she was responsible for the protection of the children, and determined that the tapping must be investigated, once and for all. Just as she was stirring, the soft sighing recommenced close to the shutters, followed by three clear taps.