`Well, I couldn't be sure of that, but I dare say my fare knew all about it. We pulled up halfway down the street and waited an hour and a half. Then the two gentlemen passed us, walking, and we followed down Baker Street and along - '

`I know,' said Holmes.

`Until we got three-quarters down Regent Street. Then my gentleman threw up the trap, and he cried that I should drive right away to Waterloo Station as hard as I could go. I whipped up the mare and we were there under the ten minutes. Then he paid up his two guineas, like a good one, and away he went into the station. Only just as he was leaving he turned round and he said: ``It might interest you to know that you have been driving Mr. Sherlock Holmes.'' That's how I come to know the name.'

`I see. And you saw no more of him?'

`Not after he went into the station.'

`And how would you describe Mr. Sherlock Holmes?'

The cabman scratched his head. `Well, he wasn't altogether such an easy gentleman to describe. I'd put him at forty years of age, and he was of a middle height, two or three inches shorter than you, sir. He was dressed like a toff, and he had a black beard, cut square at the end, and a pale face. I don't know as I could say more than that.'

`Colour of his eyes?'

`No, I can't say that.'

`Nothing more that you can remember?'

`No, sir; nothing.'

`Well, then, here is your half-sovereign. There's another one waiting for you if you can bring any more information. Good-night!'

`Good-night, sir, and thank you!'

John Clayton departed chuckling, and Holmes turned to me with a shrug of his shoulders and a rueful smile.

`Snap goes our third thread, and we end where we began,' said he. `The cunning rascal! He knew our number, knew that Sir Henry Baskerville had consulted me, spotted who I was in Regent Street, conjectured that I had got the number of the cab and would lay my hands on the driver, and so sent back this audacious message. I tell you, Watson, this time we have got a foeman who is worthy of our steel. I've been checkmated in London. I can only wish you better luck in Devonshire. But I'm not easy in my mind about it.'

`About what?'

`About sending you. It's an ugly business, Watson, an ugly dangerous business, and the more I see of it the less I like it. Yes my dear fellow, you may laugh, but I give you my word that I shall be very glad to have you back safe and sound in Baker Street once more.'