house, but, when he reached the front porch, and had seen no one, he
felt more at ease.

"Hello, Mark!" he cried boldly. "Are you inside?"

He paused for an answer. None came.

"This is getting rather strange," murmured Jack, who was now quite
puzzled as to what to make of the whole matter. "Mark must be here, yet
why doesn't he answer me? Oh, you Mark!" he shouted at the top of his
voice.

There was only silence, and, after waiting a few moments Jack made up
his mind that the best plan would be to enter the house and look
around.

He made a hasty search through the lower rooms, but saw no sign of
Mark. It was the same upstairs, and on the third floor there was no
evidence of his chum. Jack called again, but got no reply.

"The garret next, and then the cellar," he told himself, and these two
places, darker and more dismal than any other parts of the old mansion,
were soon explored.

"Well, if Mark came here he's not here now," thought Jack, "and there's
no use in my staying any longer. Maybe something happened that he had
to go back home. Perhaps he's trailing the man. We should have made up
some plan to be followed in case anything like that happened."

Deciding that the best thing he could do would be to go back home Jack