“Nellie!  Dora!  Where are you?” he called out. “Where are you?”

Only the faint breeze in the trees answered him.

“I’ve got to find them!” he groaned.  “I’ve got to!  That is all there is to it.”  He repeated the words over and over again.  “What will Mrs. Laning and Mrs. Stanhope say, and Grace?”

Again he went on, but this time slower than before, looking to the right and the left and ahead.  Not a soul was in sight.  The road was so cut up he could make nothing of the hoofmarks which presented themselves.

“This is enough to drive one insane,” he reasoned.  “Where in the world did they go to?  I’d give a thousand dollars to know.”

At last he reached a point where the road ran close to the water’s edge.  He looked out on the river.  Only a distant steamboat and a small sailboat were in view.

“Wonder if they rode down to where we left the houseboat?” he asked himself.  “She must be somewhere in this vicinity.  Maybe they have only been fooling us.”

Although Tom told himself this, there was no comfort in the surmise.  He moved on once more.  It was now growing dark and there were signs of a coming storm in the air.

At last he reached a spot which looked somewhat familiar to him.  He came down to the water’s edge once more.

“Why—­er—­I thought the houseboat was here,” he said, half aloud.  “This looks like the very spot.”

But no houseboat was there, and scratching his head once more, Tom concluded that he had made a mistake.

“I’m upset if ever a fellow was,” he thought.  “Well, no wonder.  Such happenings as these are enough to upset anybody.”

Tom knew of nothing more to do than to return to where he had left Dick, and this he did as quickly as the tired horse would carry him.

“No success, eh?” said the oldest Rover.  “What do you make of it, Tom?”

When he had heard his brother’s tale he grew unusually grave.

“You are sure you heard them scream?” he questioned, anxiously.

“I’m sure of nothing—­now.  I thought I was sure about the houseboat, but I wasn’t,” answered Tom, bluntly.  “I’m all mixed up.”

“I’ll go down there with you,” was the only answer Dick made.

It did not take long to reach the spot.  It was now dark and a mist was rising from the river.

“This is certainly the spot where we tied up,” declared the oldest Rover.  “Why, I helped to drive that stake myself.”

“Then the houseboat is gone!”

“That’s the size of it.”

“And the girls are gone too,” went on Tom.  “Yes, but the two happenings may have no connection, Tom.”

“Don’t be so sure of that!”

“What do you mean?”

“I’m thinking about Dan Baxter and Lew Flapp.  They wouldn’t be above stealing the houseboat.”

“I believe you there.”

“And if those girls happened to go on board—­Look there!”