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.