"I was going to ask you about that," Grey murmured. "I hear he is suffering from the effects of a severe fall. I hope the accident won't leave any permanent injury."
"I don't think so," the doctor said. "I had a specialist down to-day and he takes a very sanguine view of the case. All that is wanted is rest. For the moment my patient has a partial lapse of memory—a sort of hiatus of a week. In other words, he can recollect everything perfectly well, except that the past seven days are a complete blank to him. And during the last day or so before his fall he had been engaged in some experiment, the results of which ought to be placed on record at once. This seems to worry him terribly. It has affected him to such an extent that he is making himself seriously ill over it. Imagine a man who has some great commercial deal on and has to buy or sell at a given moment suddenly forgetting the very thing he has to do. That appears to be Rent's case. Anybody might suppose that he had committed murder and had forgotten to hide the clue, by the way he goes on."
A sudden exclamation broke from Grey, which he checked immediately. The doctor looked up inquiringly.
"A twinge of pain," he muttered. "Nothing much to trouble about. A most interesting case, doctor. And you think that in time Rent will be quite himself again?"
"Oh, I am certain of it. If I could only prevent him from worrying, I should have had him right by this time. Of course, what I am saying to you is in strict confidence."
Grey and Tanza gave the desired assurance, and the conversation became more general. When the doctor left he was accompanied by Grey, who said he had business on shore. He left the man of medicine at the corner of a street leading up from the quay and proceeded along the shore to Arnold Rent's workshop. He stood for a long time making a mental calculation, after which he walked several times round the building, examining the ground carefully as if in search of something. Apparently, nothing had rewarded his efforts, for he shook his head impatiently and crossed over to the office, in the window of which a light was burning. Someone inside was singing a snatch from a comic opera in a loud, blustering voice. An unsteady, flickering shadow crossed the blind once or twice, and Grey's features broke into a grim smile.
"Friend Swift has broken out again," he murmured. "What a pity so clever a man should be the victim of a curse like this! Still, his misfortune is my opportunity, and if there is anything he can tell me, now is the time to learn it."
Without further hesitation, Grey pushed his way into the office, which was flooded with half a dozen powerful electric lights. The large slate-topped table had been cleared of all kinds of electric appliances. There were the remains of a supper at one end, flanked by two or three empty bottles. The reserved and saturnine Swift seemed to have changed altogether. His dark features wore a look of reckless gaiety; his sombre eyes were shining. He did not appear to be in the least surprised to see Grey; in fact, he might have been expecting him. His unsteady gait and thick speech, however, told their tale.
"Hallo!" he exclaimed. "So you have come to pay me a visit? You have come here to learn the secrets of the prison-house? Ah, my dear fellow, you are very clever, but your tuppenny discoveries are nothing compared to what we are on the track of here. For we've got it, my boy, we've got it. You remember the dream you used to indulge in at school?"
"Intermittent electricity," Grey exclaimed. "A wireless current. You don't mean to say you have got to the bottom of that!"