included a sitting-room, though he devoted fully quarter of an hour to
reading the titles of Siddle's books.

A safe in the little dispensing closet at the back of the shop promised
sheer defiance until Furneaux saw a bunch of keys resting beside a
methylated spirit lamp.

"'Twas ever thus!" he cackled, lighting the lamp. "Heaven help us poor
detectives if it wasn't!"

In a word, since murder will out, Siddle had forgotten his keys!
Probably, he had gone to the safe for money, and, while writing the
notice as to his absence, had laid down the keys and omitted to pick
them up again.

Furneaux disregarded ledgers and account books. He examined a bank
pass-book and a check-book. In a drawer which contained these and a
quantity of gold he found a small, leather-bound book with a lock, which
no key on the bunch was tiny enough to fit. A bit of twisted wire soon
overcame this difficulty, and Furneaux began to read.

There were quaint diagrams, and surveyor's sketches, both in plan and
section, with curious notes, and occasional records of what appeared to
be passages from letters or conversations. The detective read, and
read, referring back and forth, absorbed in his task, no doubt, but
evidently puzzled.

At last, he stuffed the book into a pocket, completed his scrutiny of the
safe, examined the bottles on the shelf labeled "poisons," and took a
sample of the colorless contents of one bottle marked "C10H14N2."