"And Snap still acts queerly, whenever he pa.s.ses that locker," said Mrs. Bobbsey. "I'm not so sure it is a rat that made that noise, Richard."

"No?" her husband asked. "What was it, then?"

But Mrs. Bobbsey either could not, or would not, say.

"I say, Harry," said Bert to his country cousin one day, when the Bluebird had come to anchor some distance down the lake, "let's try to get to the bottom of this mystery."

"What mystery?"

"Why, the one about the noise, and the sandwiches and cakes being taken, and Snap acting so funny. I'm sure there's a mystery on this boat, and we ought to find out what it is."

"I'm with you!" exclaimed Harry. "What shall we do?"

"Let's sit up some night and watch that closet," said Bert. "We can easily do it."

"Will your folks let us?"

"We won't ask them. Oh, I wouldn't do anything I knew they didn't want me to do without asking," Bert said quickly, as he saw his cousin's startled glance.

"But there's no harm in this," Bert went on. "We'll go to bed early some night, and, when all the rest of them are asleep, we'll get up and stand watch all night. You can watch part of the time, and when you get sleepy I'll take my turn. Then we can see whether anything is hiding in that closet."

"Do you think there is?" asked Harry.

"I'm sure I don't know what to think," Bert answered. "Only it's a mystery, and we ought to find out what it is."

"I'm with you," said Harry again.

"Are you talking secrets?" asked Nan, suddenly coming up just then.

"Sort of," admitted her brother, laughing.

"Oh, tell me--do!" she begged.

"No, Nan. Not now," said Bert. "This is only for us boys."

Nan tried to find out the secret, but they would not tell her.

Two days later, during which the Bluebird cruised about on the lake, Bert said to Harry, after supper:

"We'll watch to-night, and find out what's, in that closet. Snap barked and growled every time to-day, that he pa.s.sed it. I'm sure something's there."

"It does seem so," admitted Harry.

Mr. Bobbsey was steering the boat toward sh.o.r.e, intending to come to anchor for the night, when Flossie, who was standing up in front cried:

"Oh, look! Here's the waterfall! Oh, isn't it beautiful!"

Just before them, as they turned around a bend in the bank, was a cataract of white water, tumbling down into the lake over a precipice of black rocks--a most beautiful sight.

CHAPTER XXI

WHAT BERT SAW

The waterfall of Lake Romano was still some little distance off, and, as the wind was blowing toward it, only a faint roar of the falling water came to the ears of the Bobbsey twins, and the others on the houseboat.

"Oh, papa!" exclaimed Nan. "May we go close up and see the cataract?"

"Yes," said Mr. Bobbsey. "I intended to give you a good view of the waterfall. We shall spend a day or so here, as it is a great curiosity. There is one place where you can walk right behind the falls."

"Behind it!" cried Harry. "I don't understand how that can be, uncle."

"You'll see to-morrow, when we visit them," said the twins' father.

"And there are some oddly-marked stones to be picked up, too, Bert.

They will do for your collection."

"Fine!" Bert exclaimed. "Say, this has been a dandy trip all right!"

"It isn't ended yet, is it, Dorothy?" asked Nan.

"No, indeed," replied the seash.o.r.e cousin, with a smile.

"And we haven't solved the mystery," said Bert in a low voice to Harry. "But we will to-night, all right."

"We sure will," agreed the boy from the country.

The Bobbsey twins stayed up rather later that night than usual. Mr.

Bobbsey did not find a good anchorage for the boat for some time, as he wanted to get in a safe place. It looked as though there might be a storm before morning, and he did not want to drift away again. Then, too, he wanted to get nearer to the waterfall, so they could reach it early the next morning and look at it more closely.

So the motor was kept in action by Captain White until after supper, and finally the Bluebird came to rest not far from the waterfall. Then Bert and Nan, with Dorothy and Harry were so interested in listening to Mr. Bobbsey tell stories about waterfalls, and what caused them, that the older twins and their cousins did not get to bed until nearly ten o'clock, whereas nine was the usual hour.

Of course Flossie and Freddie "turned in," as sailors say, about eight o'clock, for their little eyes would not stay open any longer.

"We'll wake up as soon as my father and mother are asleep," said Bert to Harry, as they went to their rooms, which were adjoining ones.

"Then we'll take turns watching that closet."

"Sure," agreed Harry. "Whoever wakes up first, will call the other."

To this Bert agreed, but the truth of it was that neither of them awakened until morning. Whether it was that they were too tired, or slept later than usual, they could not tell. But it was broad daylight, when they sat up in their beds, or "bunks," as beds are called on ships.

"I thought you were going to call me," said Bert to his cousin.

"And I thought you were going to call ME," laughed the boy from the country.

Then they both laughed, for it was a good joke on each of them.