Concealed in the booth occupied by Ned was a sending plate. It
could not be seen unless one knew just where to look for it. In
Tom's booth was a receiving plate.

The experiment did not take long. Presently Tom called to Ned that
he need stay there no longer.

"Come on to the house," invited the young inventor, "and we'll
develope this plate." For in this system it was necessary to
develope the receiving plate, as is done with an ordinary
photographic one. Tom wanted a permanent record.

Eagerly the chums in the dark room looked down into the tray
containing the plate and the developing solution.

"Something's coming out!" cried Ned, eagerly.

"Yes! And it's you!" exclaimed Tom. "See, Ned, I got your picture
over the telephone. Success! I've struck it! This is the best
yet!"

At that moment, as the picture came out more and more plainly,
someone knocked on the door of the dark room.

"Who is it?" asked Tom.

"Gen'man t' see you," said Eradicate. "He say he come from Mistah
Peters!"

"Mr. Peters--that rascally promoter!" whispered Tom to his chum.