"Here you are, Jimmy," I said, "you cut back and give the old lady my message. Just say that I've received the letter, and that I'll do exactly what Miss de Roda wishes." I conducted him to the door, stammering his thanks, and assuring me that my errand should be faithfully discharged, and having watched him hurry across the lawn and disappear into the shrubbery, I once more turned the key and shot home the bolts. I felt that if ever I had cast my bread successfully upon the waters, it was in picking out Jimmy as a trustworthy confederate. Except for him, Christine would have had no chance of sending her letter across to the island, while the news he had brought with regard to de Roda was perhaps of even greater significance than anything she had dared to write. There was only one explanation which would account for this sudden purchase of a sea-going motor-boat. Manning and de Roda must have made up their minds that the time had arrived for their final effort. Believing that I should be alone in the house that night, they had evidently decided to seize the diamonds by force and to make a bolt for the continent, where their plans were no doubt already arranged. Having become suspicious of Christine, they had apparently taken the simple course of locking her in her own room, so that she should have no possible opportunity of communicating their designs to me. The one weak point in their otherwise excellent scheme had been the old French servant. Her affection for Christine had manifestly over-ridden her fear of the others; and, while pretending to carry out their orders, she had secretly consented to assist her young mistress. If only the suggested plan worked successfully, nothing would fit in better with my own arrangements. To get Christine and de Roda into our hands was, as Campbell had said, the first and most essential step in our future proceedings. By eight-thirty, or soon after, he and Bobby ought to be back from Martlesea, and matters would be enormously simplified if they were to find half of the opening task already accomplished. I was under no delusion, however, with regard to the dangerous nature of the undertaking. Should Christine's attempt fail, she would be in greater peril than ever, while even if she succeeded it was more than probable that her escape would be immediately discovered. In that event the house might be attacked before Campbell and Bobby returned. It was impossible to foretell to an exact certainty what time they would arrive, and, with everything at stake, Manning was not the sort of gentleman to allow the grass to grow under his feet.