at they
met the centre post of the doors at an acute angle. The true side walls
were thereby exposed, and, of course, they were papered to correspond
with the rest of the interior. Their reflection was doubled in the
mirrors, making it appear to the observer that the whole cabinet was
open to his vision. The truth was that he saw only half of it, the
performer being concealed behind the mirrors. The only possible point
at which the illusion could be detected was the angle where the mirrors
joined, and this was masked by the centre post at which the double
doors met. To conclude the trick, the doors were again closed, the
performer swung the mirrors back into place, and, presto! he was back
in the cabinet, smiling genially at the gaping crowd."

"Then you think--"

"I know. Lock-box No. 82 was constructed on the same principle in
miniature, the letter-slit being placed in such a position that
anything deposited in the box fell behind the mirrors, the whole
interior remaining apparently visible through the glass front, and
presumably empty. The owner of the box would naturally glance into it
before actually using his pass-key. Obviously, it were a waste of time
to go through the form of opening an EMPTY box, and so poor Sydenham
never got any of the letters that were daily deposited there, for the
receptacle is a large one and the secret place behind the mirrors was
almost full. The action of unlocking the box operated upon an interior
mechanism that swung back the mirrors at the same instant that the door
was pulled open. After seeing my dummy disappear, I tried the
experiment, and was amply rewarded.

"There isn't much more to tell. When I saw the letters lying there I
knew that it was all right so far as the girl was concerned. I had only
to acquaint Miss Sandford with the circumstances in the case to secure
her further co-operation, for, of course, she had never ceased to
believe in her lover. She prepared and sent the message which you saw
delivered to Sydenham in Sandford's office this afternoon.

"But it was not the same as the one received by him on the actual
January 9th. That contained a word, 'yes,' and was signed by her
initials; this second one consisted simply of a sprig of heliotrope."

"Do you understand the language of flowers? The heliotrope means, 'Je
t'adore,' and Sydenham understood it instantly, as you saw."

"Yes; but why--"

"To repeat the original message would not have impressed him as I