the passage and the octagonal
room you described, as well as the tower, been shut off from all
communication with the older part of the house by a heavy iron door, of
which Mr. Wildred invariably carries the key. This his butler explained
by saying that the door had been placed on account of his master's
chemical experiments, which were sometimes of a slightly dangerous
character, unless great precautions were used, and in case of an
explosion or other accident the safety of the living-rooms might be
assured by means of the iron door. The only way of opening it would have
been to employ dynamite, the lock being impregnable; and as the grounds
for suspicion against Mr. Wildred were not yet strong enough to resort
to such violent means, there was nothing to do but wait. He was wired
for to London at once."

"Naturally he would prefer being on the spot," I said, with something
like a sneer. "All the same, I am very sure that there _is_ another
means of communicating with the octagonal room and the tower besides the
main door through the passage." And I mentioned the mysterious
disappearance of the servant, which had on Christmas Day led me to
believe in the existence of a secret way of exit.

"We did look about for something of the sort, and even went down a
cellar," said the detective, "but saw not the slightest sign to suggest
a hidden door."

"Well, go on then to Mr. Wildred's return," I exclaimed impatiently. "I
am anxious to learn why it has been decided that I put you on the wrong
track."

"When he came home he admitted very frankly that he had been annoyed at
the bother occasioned by our telegram, but appeared by that time to have
recovered from his vexation, and to be inclined to laugh the matter off.
He let us know in a moment that he guessed how the information had come,
but we said nothing, of course, to confirm his suppositions.

"In the first place he opened the iron door, explained its workings as
though he took some pride in its mechanism, which he said he had
invented himself. Then he showed us into the octagonal room, which he
had had fitted up as a studio and smoking-room combined. The little door
you had seen behind the drapery merely led into a cupboard containing
boots, an artist's model--a jointed figure of wood--and other odds and
ends. It was concealed only because it was not 'an object of beauty,'
Mr. Wildred said.

"We then proceeded to the tower, where the chemical experiments are
made.