“What factor?” Pauline demanded. “Why, your sister, of course!” he replied, with a slight smile that disclosed momentarily the quizzical male person in him. “Consider how it complicates the affair. If I had to deal only with the mysterious individual with grey hair and a blue suit--perhaps you do not know that he calls himself Jetsam?--I could go to work in a simple masculine fashion, and in the end one of us would suffer, probably he. But with a woman in the case----” “How can you be sure,” Pauline interrupted him, “that Rosie is in the case?” “Can you doubt it?” “I cannot understand why she should behave so!” “Perhaps she knew him before,” Carpentaria hazarded. “Never,” said Pauline positively--“never.” “Then he has certainly been able to exercise a most remarkable influence over her.” “Not a hypnotic influence, or anything of that kind?” “Perhaps an influence of quite another kind--quite another kind.” “But Rosie is scarcely half his age.” “Do these things depend on age?” cried Carpentaria. “They depend on glances, sympathies, and trifles even more subtle than sympathies. Besides, she is more than half his age.” “Oh,” murmured Pauline, with a sudden wistful appeal in her voice, “I shall trust you to help me, Mr. Carpentaria. Rosie may be in danger; she may be doing something very foolish, mixing herself up like this in the kidnapping of poor Cousin Ilam. What is to be done?” “She is decidedly doing something very foolish,” said Carpentaria, “foolish, that is, from a mere ordinary common-sense point of view. But I don’t think she is in any danger. I don’t think that either she or you are the sort of woman that gets into danger without very good cause. As to what is to be done, I have an idea. Mrs. Ilam will be all right alone?” “Yes; for a few hours, at any rate.” “Then will you come with me to the river? I have some investigations to make.” “Certainly,” said Pauline. And as they crossed the Oriental Gardens for the second time that night, he told her what he knew about the use, or rather the abuse, of the automobile. The marble parapet of the immense terrace of the gardens stood a dozen feet above the level of high tide. The terrace was continuous from end to end, but in several places it formed a viaduct over paths that ran from the gardens at a steep slope down to the bed of the river. It was one of these paths, a specially clayey one, at the point where it ran under the terrace, that Carpentaria suspected the automobile of having taken. Assuming his suspicion to be correct, the automobile could only have descended to the Thames, and then, if the tide gave room, turned round and returned; or, if the tide did not give room, backed out without turning. “Its sole purpose,” said Carpentaria, as they talked the matter over, “could have been to pass something to a boat. Don’t you think so?” “Yes,” Pauline agreed, and then she added, “unless they merely wanted to throw something into the river.”