"Intermittent electricity," Tanza interrupted.
"Once more, wonderful man!" Grey laughed. "That is what Bark was driving at. He wants to know all about those experiments, and no doubt it was exceedingly exasperating to discover that Rent had abandoned his researches and broken up his machinery. By a singular coincidence—at least, you and I will call it a singular coincidence—that machinery was broken up on the very day that the French maid's body was found in the fountain by the sundial. Let me tell you that it was Bark who elicited this information; in fact, he fished for it. From our point of view, this is a most important discovery, as you know. Still, it is practically the only real point that Bark made, and it turned his head to such an extent that he made the mistake of frightening his man. A moment or two later Swift bolted like a hare, and Bark remarked, sotto voce, that next time they met his man would be as wax in his hands. But if we play our cards correctly, the next time Swift has an interview with anybody it will be with us two and not with Bark. I know that Swift always works from eight till ten o'clock at night, and it struck me that the best thing we could do would be to call to-morrow night and have it out with him."
"A good idea," Tanza said. "But suppose the same idea occurs to Bark. He knows as well as we do what Swift's habits are, and there is nothing to prevent him from turning up at the interview. Wouldn't that be rather awkward?"
"Oh, it might," Grey admitted. "But I have a plan for dealing with Mr. Bark. Leave him to me. We can afford to take it easy to-morrow, and after dinner we will go as far as Rent's offices and get to the bottom of this business. We can see Rent's place from our anchorage as soon as the office is lighted up. We can go then and interview him. If you don't mind, I should like to turn in between the sheets for an hour or two, for I am dead-tired."
The two friends dined comfortably, then lingered for half an hour over a cigar, until the twilight began to fall and the houses and shops along the sea-front were picked out picturesquely with tiny points of flame. It was possible to discern the outline of Rent's workshop from the deck of the yacht, and presently Grey's quick eyes made out the square of flame which burnt so brilliantly in the office window. Swift was at work, and there was no occasion to waste further time. Tanza rose to his feet and tossed the end of his cigar into the water. He seemed alert and vigorous.
"Now I am ready if you are," he said. "I suppose there are no preparations to make. Shall we order the men to wait for us, or shall we leave it and take a shore boat back?"
"I think the men had better wait for us," Grey said. "And, if you don't mind, we'll pull round the bay and land opposite the workshop. Your boatmen may have a burden to bring back with them, so I shall be glad if you will choose two who are devoted to your interests and are not too fond of asking superfluous questions. I don't think there will be any risk in the matter, but I will take a small bottle of chloroform."
Tanza asked no questions. He gave Grey credit for knowing what he was talking about. He picked out two of the most discreet of his crew, who, he declared, were ready to commit every crime in the Decalogue, and ask no questions, if only he ordered them to do so. The boat set off presently, and was moored at length on a spit of sand opposite the low block of buildings which formed Rent's workshop. The two friends stole over the sands and made their way into the buildings. It seemed to them that there was more than one person inside, for they could hear the sound of voices, which, however, presently resolved themselves into the voice of Swift, who was singing wild snatches of incoherent verse. Grey looked at his companion significantly. Then Tanza suddenly paused and complained of the closeness of the atmosphere. A moment later a puff of acrid smoke filled the corridor, and there came the snapping sound which speaks unmistakably of fire.
"The madman!" Grey explained. "He has set the place ablaze. Come, there is no time to lose."
They burst into the main workshop, which was now full of smoke and flame. There was a heap of highly inflammable materials on the floor, round which Swift was dancing wildly, singing jubilantly as he leapt. The light of insanity blazed in his eyes. Evidently he was no longer responsible for his actions. Seizing a heavy ruler, Tanza proceeded to beat down the flames, which Grey finally extinguished with a bucket of water which he discovered under a tap in a corner of the room. Then the windows were flung open, and it was possible to breathe freely again. Swift glanced vacantly at the intruders. He did not seem to have the least idea whom he was addressing. He continued to journey round the smouldering ashes, singing and shouting in the same meaningless way.