I left the house by the window, just as I had entered it, and, walking as far as the Marylebone Road, entered a small private bar, where, being alone, I took out the scraps of half-burned paper and eagerly examined them. Alas! most of the faint-ruled pages were blank. The others, however, were covered with a neat feminine calligraphy, the words, as far as I could decipher, having reference to certain chemical experiments of the Professor’s!

Those precious notes by Ethelwynn at the Professor’s dictation had, it seemed clear, been wantonly destroyed.

What could have been the motive? If that were found, it would surely not be difficult to discover the perpetrator of that most amazing crime.

I returned home more than ever mystified, but carrying in my pocket a cabinet photograph of the dead man, which I had abstracted from a silver frame in his daughter’s boudoir. It was theft, I knew, but was not theft justifiable in such unusual circumstances?

Next morning I was early at the garage in order to carry out a plan upon which I had decided during the grey hours before the dawn. In the telephone book I searched for, and found, the Professor’s number at his seaside cottage at Broadstairs, and asked the exchange for it.

In a quarter of an hour I was informed that I was “through.”

“Is Miss Ethelwynn at home?” I inquired. “No; she’s gone out for a walk,” replied a feminine voice—that of a maid, evidently. “Who are you, please?”

“Mr Kershaw Kirk,” I replied, for want of something better to say.

“Oh, Mr Kirk!” exclaimed the woman. “Is that you, sir? Your voice sounds so different over the ’phone. Miss Ethelwynn left word that, if you rang up, I was to tell you that Mr Langton is back, so you had better keep out of the way.”

“What does Langton know?” I asked, quickly on the alert.