“What’s that?” asked Aunt Josephine, in surprise.

Just then Elaine and Lieutenant Woodward came in and stopped before the tent.  Aunt Josephine motioned to Elaine to come in and Elaine followed.  Lieutenant Woodward started after her.

“No, no, young man,” laughed Ancient Anna, shaking her forefinger at him, “I don’t want you.  It’s the pretty young lady I want.”

Woodward stood outside, though he did not know quite what it was all about.  While he was standing there, Professor Arnold came up.  He had not exactly made a hit with the guests.  At least, he seemed to make little effort to do so.  He and Woodward walked away, talking earnestly.

In the tent Aunt Josephine handed Elaine the piece of paper she had picked up.

“What does it mean?” asked Elaine, studying the curious drawing in surprise.

“I’m sure I don’t know,” confessed Aunt Josephine.

“Nor I.”

Meanwhile Lieutenant Woodward and his friend had moved to a corner of the veranda and stood looking intently into the moonlight.  There was Del Mar deep in conversation with a man who had slipped out, at a quiet signal, from his hiding-place in the shrubbery.

“That fellow is up to something, mark my words,” muttered Arnold under his breath.  “I’d like to make an arrest, but I’ve got to have some proof.”

They continued watching Del Mar but, so far at least, he did nothing that would have furnished them any evidence of anything.

So the party went on, most merrily until, long after the guests had left, Elaine sat in her dressing-gown up in her room, about to retire.

Her maid had left her and she picked up the slip of paper from her dresser, looking at it thoughtfully.

“What can a crude drawing of a sunrise on the sea mean?” she asked herself.

For a long time she studied the paper, thinking it over.  At last an idea came to her.

“I’ll bet I have it,” she exclaimed to herself.  “Something is going to happen on the water at sunrise.”

She took a pretty little alarm clock from the table, set it, and placed it near her bed.

Returning from the party to his library, Del Mar entered.  Except for the moonlight streaming in through the windows the room was dark.  He turned on the lights and crossed to the panel in the wall.  As he touched a button the panel opened.  Del Mar switched off the lights and went through the panel, closing it.

Outside, at the other end of the passageway, was one of his men, waiting in the shadows as Del Mar came up.  For a moment they talked.  “I’ll be there, at sunrise,” agreed Del Mar, as the man left and he reentered the secret passage.

While he was conferring, at the library window appeared a face.  It was Professor Arnold’s.  Cautiously he opened the window and listened.  Then he entered.

First he went over to the door and set a chair under the knob.  Next he drew an electric pocket bull’s-eye and flashed it about the room.  He glanced about and finally went over to Del Mar’s desk where he examined a batch of letters, his back to the secret panel.