“Seen anything more of the ghost?” asked Will of the girls, when the canoe had been moored to the shore.

“No, and we don’t want to,” returned Betty.

“Afraid?” Allen wanted to know.

“Indeed not!” she exclaimed, with a blush.

“I’ll tell you what let’s do,” suggested Frank.  “Let’s take a look around and see if that ghost left any footprints.”

“Ghosts never do,” asserted Will.

“Well, let’s have a look anyhow.  We should have done it before.  Now, as nearly as I can recollect, the creature came about to here, and then rushed into the lake,” and Frank went to a spot some distance from the tents.  The others agreed that it was about there that the white object had been seen.  Will was looking along the ground, going toward the lake.  Suddenly he uttered an exclamation.

“Girls!  Fellows!” he cried.  “Come here!” They all hastened to his side.  He pointed to some marks in the sandy soil.

“What are they?” he asked, excitedly.

“Hoof marks!” cried Allen, dramatically.

“That’s right!” agreed Will.  “They are the marks of a horse!  Girls, that’s what your ghost is—­ a white horse, and—­ and——­ "

He ceased abruptly, looked at Grace strangely, and then brother and sister gasped together: 

“Prince!”

“What?” demanded Allen.

“I’ll wager almost anything that this ghost is my white horse, Prince, that has been missing so long!” went on Will.  “But how in the world he could have gotten on this island, so far from the mainland, is a mystery!”

“Couldn’t he swim?” asked Frank.

“Of course!” cried Will.  “I forgot about that.  And Prince was once a circus horse, or at least in some show where he had to jump into a tank of water.  Prince is a regular hippopotamus when it comes to water.  Strange I never thought of that before!

“But this solves the ghost mystery, girls.  You and the other folks have been frightened by white Prince scooting about the island.”

“We—­ we weren’t so very frightened,” spoke Mollie.

“But the rattling chains?” questioned Grace.

“What were they?”

“The stirrups, of course,” answered her brother.  “And, by Jove, Grace, if the stirrups are on Prince the saddle must be on him also, and the papers——­ "

“Oh, isn’t this just fine!” cried Grace, her face alight.  “Now papa can complete that business deal.  I never loved a ghost before.  Dear old Prince!”

“Of course we are assuming a lot,” said Will.  “It may not be Prince after all, but all signs point to it.  He must have been on this island all the while.  No wonder we could get no trace of him.  Probably he was so frightened at the storm and the auto, and his fall, that he ran on until he came to the lake.  Then his old training came back to him, and in he plunged.  There’s enough fodder here for a dozen horses.  He’s just been running wild.  I’ll have my own troubles with him when I get him back.”