The panel in the wall of his library opened and in the still dripping submarine suit, holding under his arm the weird helmet, Del Mar entered.  No sooner had he begun to remove his wet diving-suit than the man who had signalled with the heliograph that we had found Del Mar’s message from “below,” whatever that might mean, entered the house and was announced by the valet.

“Let him come in immediately,” ordered Del Mar, placing his suit in a closet.  Then to the man, as he entered, he said, “Well, what’s new?”

“Quite a bit,” returned the man, frowning still over Elaine’s accidental discovery of the under-water communication.  “The Dodge girl happened to pick up one of the tubes with a message just after you went down.  I tried to get her by blowing up the bridge, but it didn’t work, somehow.”

“We’ll have to silence her,” remarked Del Mar angrily with a sinister frown.  “You stay here and wait for orders.”

A moment later he made his way down to a private dock on his grounds and jumped aboard a trim little speed boat moored there.  He started the motor and off the boat feathered in a cloud of spray.

It was only a moment by water before he reached the Dodge dock.  There he tied his boat and hurried up the dock.

. . . . . . .

Elaine and I arrived home without any further experiences after our hairbreadth escape from the explosion at the bridge.

We were in doubt at first, however, just what to do about the mysterious message which we had picked up in the harbor.

“Really, Walter,” remarked Elaine, after we had considered the matter for some time, “I think we ought to send that message to the government at Washington.”

Already she had seated herself at her desk and began to write, while I examined the metal tube and the note again.

“There,” she said at length, handing me the note she had written.  “How does that sound?”

I read it while she addressed the envelope.  “Very good,” I replied, handing it back.

She folded it and shoved it into the envelope on which she had written: 

  Chief,
     Secret Service,
        Washington, D. C.

I was studying the address, wondering whether this was just the thing to do, when Elaine decided the matter by energetically ringing the bell for Jennings.

“Post that, Jennings, please,” she directed.

The butler bowed just as the door-bell rang.  He turned to go.

“Just a minute,” I interrupted.  “I think perhaps I’d better mail it myself, after all.”

He handed me the letter and went out.

“Yes, Walter,” agreed Elaine, “that would be better.  Register it, too.”

“How do you do?” greeted a suave voice.

It was Del Mar.  As he passed me to speak to Elaine, apparently by accident, he knocked the letter from my hand.

“I beg your pardon,” he apologized, quickly stooping and picking it up.