"Helena most imprudently left the case on her dressing-table last night," he said, "and owing to the heat she kept the window open. Some one must have waded into the water in the dark and stolen it. Perhaps one of the bandsmen may have noticed the flashing of the diamonds on her wrist and returned to secure the bracelet--there's no saying. The only too palpable fact is that it is gone--it was valued at twenty thousand pounds!" "Have you sent for the police?" I asked. "Yes, and have also wired to Scotland Yard for one of their best detectives. Vyner took the telegram for me, and was to call at the police station on his way back. He is nearly as much upset as I am. This is a terrible loss. I feel fit to kill myself for my folly in bringing that valuable bracelet on board a house-boat." "It was a little imprudent," I answered, "but you are sure to get it back." "I hope so," he replied moodily. Just then the punt with Vyner and a couple of policemen on board was seen rapidly approaching. Ridsdale went to meet them, and was soon in earnest conversation with the superintendent of police. The moment Vyner leapt on board he came to the part of the deck where I was standing. "Ah, Bell," he cried, "what about my prognostications of last night?" "They have been verified too soon," I answered. I gave him a quick glance. His eyes looked straight into mine. "Have you any theory to account for the theft?" I asked. "Yes, a very simple one. Owing to the heat of the evening the Countess slept with her window open. It was an easy matter to wade through the water, introduce a hand through the open window and purloin the diamonds." "Without being seen by any occupants of the tents?" I queried. "Certainly," he answered, speaking slowly and with thought. "Then you believe the thief came from without?" "I do." "What about your warning to Lady Ridsdale yesterday evening not to trust her maid?" I saw his eyes flash. It was the briefest of summer lightning that played in their depths. I knew that he longed to adopt the suggestion that I had on purpose thrown out, but dared not. That one look was enough for me. I had guessed his secret. Before he could reply to my last remark Lord Ridsdale came up. "What is to be done?" he said; "the police superintendent insists on our all, without respect of persons, being searched." "There is nothing in that," I said; "it is the usual thing. I will be the first to submit to the examination."