"Why, some one went aboard the boat," explained Mr. Bobbsey, "and I
think it must have been some boys, for I found this cap," and he held
up a gray one.

"Why!" cried Bert when he saw it. "That's Danny Rugg's cap!"

"I thought so," went on Mr. Bobbsey. "Danny, and some of his chums,
must have gone on the boat early this evening. They played about, as
boys will, and some of them, either on purpose or accidentally, must
have loosed the knots in the ropes before coming ashore. Then the boat
just drifted away after that."

"Those boys had no right to go on our boat!" said Nan.

"No, they had not," agreed her father, "But I'm glad there was no real
damage done. The watchman saw the Bluebird soon after she had drifted
away from the dock, and he telephoned me. I went out in one of our
tugs and soon brought her back. So you think this is Danny Rugg's cap,
Bert?"

"I'm sure of it, yes, sir. Danny wanted me to take him, and some of
the other boys, on the boat, but I wouldn't."

"I'm glad you remembered what I told you," spoke Mr. Bobbsey, and Bert
blushed with pleasure.

"I'll give Danny his cap in the morning," Bert went on. "It may
surprise him to know where he lost it."