complete his observations, the spy turned from
the window and walked toward a large, flat desk in the centre of the
room. Willie shrank close against the tree and remained as motionless
as a stone image. But the spy never once glanced out of the window.
He sank into a chair before the desk, switched on an electric desk
light, and began to write on a piece of paper. Evidently he was
arranging his message. When this was done to his satisfaction, he
reached into the desk and drew forth a dollar. Willie could see it
plainly as the spy laid it on his desk blotter, under the lamp.
Intently Willie strained forward. The spy leaned forward and fumbled
about the bottom of his desk. His hands and arms were hidden and
Willie could only conjecture what was happening. Then Willie gave a
little gasp of surprise as the spy straightened up and laid on the
blotter beside the dollar a curious little thing like nothing Willie
had ever seen. Evidently it was of metal for it shone under the light.
Willie screwed up his face as he strained his eyes to identify the
object. It seemed to be a disc of exactly the same size as the dollar.
Yet it was not solid, because Willie could see the blotter through it.
To Willie the thing resembled nothing so much as a spider-web. What it
was, Willie could not even guess.

Meantime the spy had pulled open a drawer, from which he took a slender
instrument, which also Willie could not identify. But evidently it had
a sharp point; for the spy, after placing the disc on the dollar,
scratched the milled edge of the coin with the little instrument, then
he began to make marks here and there through the little disc, on the
surface of the dollar. From time to time he turned the coin, and
occasionally he looked at the writing on his paper. He seemed quite
expert, for he worked fast. He finished his task and leaned over
behind his desk, evidently to put the curious disc in its secret
repository.

Quick as a flash, Willie slid from his exposed perch and safely gained
the concealing shelter of the lower tree tops before the spy
straightened up again. Willie climbed on down the tree and joined Roy
at the usual observation post.

"What did you see?" asked Roy eagerly.

When Willie had told him, Roy groaned. "Gee! That makes it all the
harder. Now we've got to get one of those discs as well as a marked
dollar before we can discover how they send their messages."

The grocer's boy came and went. R