At this moment the little brass knocker on the inner door--the outer
oak being open--uttered a timid and apologetic rat-tat.

"Who the deuce can that be?" muttered Thorndyke, replacing the
microscope on the table. He strode across to the door and opened it
somewhat brusquely, but immediately whisked his hat off, and I then
perceived a lady standing on the threshold.

"Dr. Thorndyke?" she inquired, and as my colleague bowed, she continued,
"I ought to have written to ask for an appointment but the matter is
rather urgent--it concerns Mr. Reuben Hornby and I only learned from him
this morning that he had consulted you."

"Pray come in," said Thorndyke. "Dr. Jervis and I were just setting out
for Scotland Yard on this very business. Let me present you to my
colleague, who is working up the case with me."

Our visitor, a tall handsome girl of twenty or thereabouts, returned my
bow and remarked with perfect self-possession, "My name is Gibson--Miss
Juliet Gibson. My business is of a very simple character and need not
detain you many minutes."

She seated herself in the chair that Thorndyke placed for her, and
continued in a brisk and business-like manner--

"I must tell you who I am in order to explain my visit to you. For the
last six years I have lived with Mr. and Mrs. Hornby, although I am no
relation to them. I first came to the house as a sort of companion to
Mrs. Hornby, though, as I was only fifteen at the time, I need hardly
say that my duties were not very onerous; in fact, I think Mrs. Hornby