I was so much excited and elated by my own ingenuity in having formed an intelligible and practicable theory of the crime, that I was now impatient to reach home that I might impart my news to Thorndyke and see how they affected him.  But as I approached the centre of the town the fog grew so dense that all my attention was needed to enable me to thread my way safely through the traffic; while the strange, deceptive aspect that it lent to familiar objects and the obliteration of landmarks made my progress so slow that it was already past six o’clock when I felt my way down Middle Temple Lane and crept through Crown Office Row towards my colleague’s chambers.

On the doorstep I found Polton peering with anxious face into the blank expanse of yellow vapour.

“The Doctor’s late, sir,” said he.  “Detained by the fog, I expect.  It must be pretty thick in the Borough.”

(I may mention that, to Polton, Thorndyke was The Doctor.  Other inferior creatures there were, indeed, to whom the title of “doctor” in a way, appertained; but they were of no account in Polton’s eyes.  Surnames were good enough for them.)

“Yes, it must be,” I replied, “judging by the condition of the Strand.”

I entered and ascended the stairs, glad enough of the prospect of a warm and well-lighted room after my comfortless groping in the murky streets, and Polton, with a final glance up and down the walk reluctantly followed.

“You would like some tea, sir, I expect?” said he, as he let me in (though I had a key of my own now).

I thought I should, and he accordingly set about the preparations in his deft methodical way, but with an air of abstraction that was unusual with him.

“The Doctor said he should be home by five,” he remarked, as he laid the tea-pot on the tray.

“Then he is a defaulter,” I answered.  “We shall have to water his tea.”

“A wonderful punctual man, sir, is the Doctor,” pursued Polton.  “Keeps his time to the minute, as a rule, he does.”

“You can’t keep your time to a minute in a ‘London Particular,’” I said a little impatiently, for I wished to be alone that I might think over matters, and Polton’s nervous flutterings irritated me somewhat.  He was almost as bad as a female housekeeper.

The little man evidently perceived my state of mind, for he stole away silently, leaving me rather penitent and ashamed, and, as I presently discovered on looking out of the window, resumed his vigil on the doorstep.  From this coign of vantage he returned after a time to take away the tea-things; and thereafter, though it was now dark as well as foggy, I could hear him softly flitting up and down the stairs with a gloomy stealthiness that at length reduced me to a condition as nervously apprehensive as his own.

CHAPTER VIII

A SUSPICIOUS ACCIDENT