e found
that the opening which it had occupied was filled by a sheet of plain
glass, evidently placed there as a precaution to prevent any person from
walking through from one closet into the other, and so discovering the
trick.

"It's all very puzzling," said Mr. Brodribb; "I don't clearly understand
it now."

"Let us finish here," replied Thorndyke, "and then I will explain.
Notice this black curtain. When I pull the second cord, it slides across
the closet and cuts off the light. The mirror now reflects nothing into
the other closet; it simply appears dark. And now I pull the third
cord."

He did so, and the mirror swung noiselessly back into its place.

"There is only one other thing to observe before we go out," said
Thorndyke, "and that is this other mirror standing with its face to the
wall. This, of course, is the one that Fred Calverley originally saw at
the end of the closet; it has since been removed, and the larger
swinging glass put in its place. And now," he continued, when we came
out into the room, "let me explain the mechanism in detail. It was
obvious to me, when I heard poor Fred Calverley's story, that the mirror
was 'faked,' and I drew a diagram of the probable arrangement, which
turns out to be correct. Here it is." He took a sheet of paper from his
pocket and handed it to the lawyer. "There are two sketches. Sketch 1
shows the mirror in its ordinary position, closing the end of the
closet. A person standing at A, of course, sees his reflection facing
him at, apparently, A 1. Sketch 2 shows the mirror swung across. Now a
person standing at A does not see his own reflection at all; but if some
other person is standing in the other closet at B, A sees the reflection
of B apparently at B 1--that is, in the identical position that his own
reflection occupied when the mirror was straight across."

"I see now," said Brodribb; "but who set up this apparatus, and why was
it done?"

"Let me ask you a question," said Thorndyke. "Is Alfred Calverley the
next-of-kin?"

"No; there is Fred's younger brother. But I may say that Fred has made
a will quite recently very much in Alfred's favour."

"There is the explanation, then," said Thorndyke. "These two scoundrels
have conspired to drive the poor fellow to suicide, and Raggerton was
clearly the leading spirit. He was evidently concocting some story with
which to work on poor Fred's superstitions when the mention of the
Chinaman on the steamer gave him