Diana's mouth closed firmly and a new keenness came into her steady eyes. It was one thing to go back voluntarily to make terms with the men who had attacked her party; it was quite another thing to be deliberately chased across the desert by an Arab freebooter. Her obstinate chin was almost square. Then the shadow of a laugh flickered in her eyes and curved her mouth. New experiences were crowding in upon her to-day. She had often wondered what the feelings of a hunted creature were. She seemed in a fair way of finding out. She had always stoutly maintained that the fox enjoyed the run as much as the hounds; that remained to be proved, but, in any case, she would give this hound a run for his money. She could ride, and there seemed plenty yet in the frightened animal under her. She bent down, lying low against his neck with a little, reckless laugh, coaxing him with all her knowledge and spurring him alternately. But soon her mood changed. She frowned anxiously as she looked at the last rays of the setting sun. It would be dark very soon. She could not go chasing through the night with this tiresome Arab at her heels. The humour seemed to have died out of the situation and Diana began to get angry. In the level country that surrounded her there were no natural features that could afford cover or aid in any way; there seemed nothing for it but to own herself defeated and pull up--if she could. An idea of trying to dodge him and of returning of her own free will was dismissed at once as hopeless. She had seen enough in her short glimpse of the Arabs' tactics when they had passed her to know that she was dealing with a finished horseman on a perfectly trained horse, and that her idea could never succeed. But, perversely, she felt that to that particular Arab following her she would never give in. She would ride till she dropped, or the horse did, before that. The whistle came again, and again, in spite of her relentless spurring, her horse checked his pace. A sudden inspiration came to her. Perhaps it was the horse she was riding that was the cause of all the trouble. It was certainly the Arab's whistle that had made it moderate its speed; it was responding clearly to a signal that it knew. Her guide's reluctance to give any particulars of his acquisition of the horse came back to her. There could not be much doubt about it. The animal had unquestionably been stolen, and either belonged to or was known to the party of Arabs who had met them. The _naivete_ that paraded a stolen horse through the desert at the risk of meeting its former owner made her smile in spite of her annoyance, but it was not a pleasant smile, as her thoughts turned from the horse to its present owner. The sum of Mustafa Ali's delinquencies was mounting up fast. But it was his affair, not hers. In the meantime she had paid for the horse to ride through the desert, not to be waylaid by Arab bandits. Her temper was going fast.