I had not yet had time to say good-bye myself when a slight exclamation at my side startled me.  Turning suddenly, I saw a very brisk, fussy old gentleman who had evidently been hurrying through the crowd.  He had slipped on something on the sidewalk and lost his balance, falling near us.

We bent over and assisted him to his feet.  As I took hold of his hand, I felt a peculiar pressure from him.  He had placed something in my hand.  My mind worked quickly.  I checked my first impulse to speak and, more from curiosity than anything else, kept the thing he had passed to me surreptitiously.

“Thank you, gentlemen,” he puffed, straightening himself out.  “One of the infirmities of age.  Thank you, thank you.”

In a moment he had bustled off quite comically.

Again Del Mar said good-bye and I did not urge him to stay.  He had scarcely gone when I looked at the thing the old man had placed in my hand.  It was a little folded piece of paper.  I opened it slowly.  Inside was printed in pencil, disguised: 

“Be careful.  Watch him.”

I read it in amazement.  What did it mean?

. . . . . . .

At the La Coste, Del Mar was met by two of his men in the lobby and they rode up to his room.

Imagine their surprise when they opened the door and found the valet lying bound on the floor.

“Who the deuce did this?” demanded Del Mar as they loosened him.

The valet rose weakly to his feet.  “A little old man with gray whiskers,” he managed to gasp.

Del Mar looked at him in surprise.  Instantly his active mind recalled the little old man who had fallen before us on the street.

Who—­what was he?

“Come,” he said quickly, beckoning his two companions who had come in with him.

Some time later, Del Mar’s car stopped just below the Dodge house.

“You men go around back of the house and watch,” ordered Del Mar.

As they disappeared he turned and went up the Dodge steps.

. . . . . . .

I walked back after my strange experience with the fussy little old gentleman, feeling more than ever, now that Craig was gone, that both Elaine and Aunt Josephine needed me.

As we sat talking in the library, Rusty, released from the chain on which Jennings kept him, bounded with a rush into the library.

“Good old fellow,” encouraged Elaine, patting him.

Just then Jennings entered and a moment later was followed by Del Mar, who bowed as we welcomed him.

“Do you know,” he began, “I believe that the lost torpedo model is somewhere in this house and I have reason to anticipate another attempt of foreign agents to find it.  If you’ll pardon me, I’ve taken the liberty of surrounding the place with some men we can trust.”

While Del Mar was speaking, Elaine picked up a ribbon from the table and started to tie it about Rusty’s neck.  As Del Mar proceeded she paused, still holding the ribbon.  Rusty, who hated ribbons, saw his chance and quietly sidled out, seeking refuge in the conservatory.