"It's a deeper remark than you are aware of at present," Bell replied. "I
quite see your position. Nobody would believe you, of course. But why not
go to the post-office and ask the number of the telephone that called you
up from London?"

The question seemed to amuse David slightly. Then his lips were drawn
humorously.

"When my logical formula came back I thought of that," he said. "On
inquiring as to who it was rang me up on that fateful occasion I learnt
that the number was 0017 Kensington and that--"

"Gates's own number at Prince's Gate," Bell exclaimed. "The plot
thickens."

"It does, indeed," David said, grimly. "It is Wilkie Collins gone mad,
Gaboriau _in extremis_, Du Boisgobey suffering from _delirium tremens_.
I go to Gates's house here, and am solemnly told in the midst of
surroundings that I can swear to that I have never been there before;
the whole mad expedition is launched by the turning of the handle of a
telephone in the house of a distinguished, trusted, if prosaic,
citizen. Somebody gets hold of the synopsis of a story of mine, Heaven
knows how--"

"That is fairly easy. The synopsis was short, I suppose?"

"Only a few lines, say 1,000 words, a sheet of paper. My writing is very
small. It was tucked into a half-penny open envelope--a mazagine office
envelope, marked 'Proof, urgent.' There were the proofs of a short story
in the buff envelope."