"Then perhaps I had better take it," and he held out his hand. "No, I'll keep it--you needn't be anxious," I said. "I have been staying here, and probably it belongs to somebody in the house, or to somebody who has called." I fumbled in my pocket and produced two half-crowns, which at once allayed any conscientious squeamishness afflicting the driver at the thought of handing over his treasure-trove to a stranger. But where was Vera? Where, indeed, were the Thorolds? The chauffeur continued to overhaul his engine and its complicated mechanism. While he was thus engaged I poured a little of the fluid out of the flask, which was quite full. The colour was a dark, transparent brown, almost the shade of old brandy. Somehow I could not help thinking that this flask might-- And yet, why should it prove a clue? What reason was there to suppose it had been dropped by the strange visitor on the previous day, the mysterious Smithson? "Hullo, sir, this is curious!" My driver was bending over the machinery he had been examining so closely. His hands, which had previously been in the gear-box resembled a nigger's, only they looked more slimy. "What is it?" I asked, approaching him. "The plugs have been tampered with. No wonder she wouldn't start. Look." He was holding out a damaged sparking-plug. I own a car and, being well acquainted with its intricacies, saw at once that what he said was true. Somebody--presumably while he was wandering about the lawns and back premises--must have lifted the bonnet and injured the plugs. There was no other solution. The car could not have travelled out from Oakham, or travelled at all, had that damage been done before. We looked at each other, equally puzzled. "You ain't been playing me a trick, sir?" he said suddenly, an expression of mistrust coming into his eyes. "Oh, don't be a fool!" I answered irritably. He turned sulky. "Some one 'as, anyway," he grunted. "And it's just a chance I've some spare plugs with me." He produced his tool-box, rummaged among its contents with his filthy hands, discovered what he wanted, and adjusted them. Then he shut down the bonnet with a vicious bang and set his engine going. He was about to step on to his seat, when simultaneously a sharp report a good way off and the "zip" of a bullet close to us made us spring away in alarm. Together, without uttering a word, we gazed up towards the wood on the hill, where the sound of the report had come from. Another shot rang out. This time the bullet shattered the car headlight. "Ah! God!" the driver gasped. "Help! I--I--" Poor fellow. Those were his last words. Almost as he uttered them there came a third report, and the driver, shot through the head, collapsed into a heap beside the car. And then, what I saw as I turned sharply, sent a shiver through me. I held my breath. What further mystery was there? Surely some great evil had fallen upon the house of the Thorolds. CHAPTER THREE.