've carried your father through some secret passage," exclaimed
Locke. "That would explain much that is strange that has happened about
the house, too."

Just then Zita stepped forward with the plan in her hand. "See," she
cried, "there is a secret passage marked on this."

Locke studied the plan for some time, but whoever had drawn it had
carefully concealed both the exact location of the passage and the
method by which it was reached. As he searched, however, an idea
occurred to Locke.

"I'll rig a trap with a camera," he decided, finally.

A few minutes later he returned to the room with his special
quick-shutter camera, a flash-bag, and a ball of light twine. Carefully
he focused the camera on the wall where the plan showed the secret
passage to be. Then he rigged up the flash-bag and connected the whole
with the twine, which he strung all about the Graveyard of Genius, so
that, should any part of the wall move, it would cause the twine to
break which in turn would at the same time release the shutter of the
camera and explode the powder of the flashlight. Thus, without any
direct human agency, a photograph would be taken.

Next he attached wires and ran them to the library above, where he
installed an annunciator, the needle of which would indicate when the
trap was sprung and the picture taken. Fascinated, the two girls
watched. Eva was almost fainting with grief at the terrible fate that
had overtaken her father. Even in his sickness, at least she had had
him. But now he was gone--to what she could only guess. Locke tried to
console her as they paced the library above, even though he realized
that such consolation was hollow.

It was perhaps half an hour later when suddenly the needle of the
annunciator began to vibrate rapidly. All leaped to their feet and ran
down the stairs to the Graveyard.

At once Locke rushed to the camera, put in a slide, and took out the
plate-holder. Then they hurried up to his laboratory.

There Locke procured a developing-bag and started to work. Nervously and
impatiently Eva and Zita watched him at his task.

At last the negative was ready and Locke drew it from the bag and held
it to the light.

There, glaring out of the plate, was the devilish face of Balcom!

Eva and Zita both uttered a cry of astonishment and consternation. Even
Locke was amazed. But the strongest feeling he had was anger as he
turned to them.

"You two take this plan," he exclaimed. "It shows a de