Experiment? It was a plain case of being out of his head. She hoped that Helen would come soon, as she always brought him around if he gave signs of delirium. Meanwhile, she must be on the watch lest he tear off his bandages, as other of Bricktop's patients had done, but her apprehensions were quite groundless. The downfall of the tray was a test after vague intimations that sound was entering Phil's silent world. It was as loud to his ears as the crackling of a sheet of newspaper. His elation over the discovery was so great that he had a reaction when the nerve-devils began plying him with their scepticism. "Well-known psychological illusion!" they said, using professional language which they had picked up from long association with hospitals. "Imagination played you a trick. You knew it was going to crash!" Very likely they were right. Hadn't he imagined that he could see the interior of the ward and how Henriette looked when she bent over him to write on his arm? Hadn't he sometimes heard her steps in imagination around his chair? He set all his mind into his ears, straining for some other sound. There was none. "This torture is called hope unfilled!" chirruped the nerve-devils. "Oh, what a dance we shall give you to-morrow after the operation! The operation is to-morrow, isn't it?" Of course the nurse related the whole affair to Helen when she arrived. "'Experiment,' he said. How extraordinary!" exclaimed the nurse, who was still more astounded when Helen gave an outcry of joy and, leaning over, puckered her lips and uttered a sharp whistle--which was one of her accomplishments--in Phil's ear. Here was real test! No imagination about this, if he had heard. She drew back, quivering with suspense. Phil was wiggling his foot almost violently for his pad and pencil. "Did somebody whistle in my ear?" he asked. "I did! I did!" she repeated wildly, as she wrote her reply. "They said it was imagination"--she knew who "they" were, those "Boches" of nerve-devils. "Score one for the Allies!" she wrote on his arm. "I'm off to tell Mr. Ears!" The Great Man came swinging along the gravel path, half running to keep up with Helen. After the scientific test which he promptly applied he felt as triumphant as a brigadier who had taken the first line trenches on a front of a thousand yards in the Ypres salient. "Only a question of time, he says," Helen wrote. "Hurrah!" Phil replied. "If anybody has a steam siren handy and blew it in my ear it would be all the more comforting." "Soon I shall not have to write on your arm any more," she told him. "That will be odd." "Yes, very!" she said. Mr. Ears had gone to tell Bricktop, who said that it would hearten Phil for the operation the next day and then despatched a messenger to the parents and Peter Smithers. The news travelled fast about the hospital. It was across the street with the Trucklefords in half an hour.