The curious thing was that she went directly to the large oblong stone, and with a great effort, lifted it up in her arms, tottered with it to the boat, and deposited it therein. Carpentaria perceived then that the stone was not a stone, but one of the coffers in which was kept the gold of the City of Pleasure. He perceived also that, attached to the coffer, was a dozen feet or so of rope with a cork float at the end. Rosie followed the coffer into the boat, pushed off, and then, at a distance of a few yards from the shore, pitched the coffer into the river. This done, she landed, made fast the painter of the boat to an iron ring in the wall of the embankment and departed; and she did it all rather neatly. Immediately she had disappeared under the terrace, Pauline cried, starting up: “I must go to her--I must ask her what she means by doing such things.” “Pardon me,” said Carpentaria; “you must do nothing of the kind. I most seriously beg you to do nothing of the kind. By interfering now you may spoil the coup which we may ultimately make.” “I don’t quite comprehend you,” Pauline observed. “Miss Dartmouth,” he addressed her excitedly, “there can be no doubt in your mind now that your sister is concerned in this plot, whatever it is. I am perfectly convinced that her motives are good, honourable, kind-hearted. But she is concerned in it. We must, therefore, so far as we can, treat her as one of the conspirators----” “But surely----” “Always with profound respect,” said Carpentaria. “Had the person in the boat been any other than your sister, should we have revealed ourselves? Certainly not! We should have followed the plot to its next development, with this advantage--that we knew something which the conspirators imagined to be a secret. The fact that the person in the boat was your sister must not alter our course of conduct. And permit me to add, Miss Dartmouth, that you first approached me on behalf of _my_ sister. We owe something to her, do we not?” “Yes,” said Pauline in a low voice. “Then what do you mean to do next?” “I suggest that we go back to your house, to see whether your sister has returned. May I ask whether, when you last spoke to her, she gave you to understand that she meant to stay with Mrs. Ilam?” Pauline breathed a reluctant affirmative. “No hint that she was going out?” “None. And----” “And what?” “Oh, dear!” Pauline sighed. “Must I tell you? Yes, I must! I’m sure Rosie is acting for the best, but really it was not her turn to watch Mrs. Ilam to-night.” “Whose turn was it?” “The nurse’s.” “And your sister changed the rotation?” “Yes. She said the nurse needed a holiday, and told her she could go away for twenty-four hours, and that she would take her place.” “What time was that?” “About six o’clock this evening, I think.” “And where has the nurse gone?” “The nurse has gone to a concert at Queen’s Hall, and will sleep at the house of some friends at Islington.”