Grace made a motion to her chums to keep silent about the whole affair, and let her answer.  She had her reasons.

“There was no report of any girl being seriously hurt at the time you mention,” she said, a trifle coolly, “but a little child was knocked down by a horse—­ a white horse.  It may have been the one you scared.”

“But unintentionally—­ unintentionally!  I hope you believe that!” said Mr. Stone earnestly.

“Oh—­ yes—­ of course,” and Grace’s voice was not quite so cold now.  She could readily understand that the accident could have happened in just that way, and it was beginning to look so.  Certainly, not knowing the girls, the young man could have no object in deceiving them,

“A little child knocked down, you say!” exclaimed Mr. Kennedy.  “I hope it was not badly hurt.  Who was it?”

“My——­” began Mollie, and she was on the point of saying it was her sister Dodo, when from the lake there sounded the cry of: 

“Fire!  Fire!  Fire!”

Then came a sharp explosion.  Everyone arose, and Mr. Kennedy exclaimed excitedly: 

“That must be an explosion on a motor boat.  Come on, Harry.  We may he needed!”

They rushed through the bushes toward the place whence the alarm came, the girls following as fast as they could.

“Don’t let him know it was I, or that it was your sister who was hurt!” Grace cautioned her chums.  “I am going to write to papa, and he can make an investigation.  Their explanation sounds all right, but they may have the papers after all.  I’m going to write to-day.”

“I would,” advised Aunt Kate.”  “It may amount to nothing, but it can do no harm to let your father know.  And I think it wise not to let these young men know that you were in that runaway.  If they really were not careless, as it seemed at first, you can tell them later, when you see how the investigation by Mr. Ford turns out.”

“That will be best,” spoke Betty.  “Oh, see, it is a boat on fire!”

They had reached a place where they could see a small motor boat, not far from shore, wrapped in a pall of black smoke, through which could be observed flickering flames.

“There—­ he’s jumped!” cried Mollie, as a figure leaped from the burning craft.  “He’s safe, anyhow.”

“There go Mr. Kennedy and Mr. Stone in their boat!” exclaimed Grace, as the slender racing craft shot out from shore.

Whatever may have been the faults of the young men as motorists, they knew how to act promptly in this case.  As they passed the man who had leaped from the burning boat they tossed him a life preserver.

Then, nearing the burning boat, they halted their own, and began using a chemical extinguisher—­ the only safe thing save sand with which to fight a gasoline blaze.  The fire did not have a chance to get much headway, and it was soon out, another boat coming up and lending aid.

The man who had jumped was taken aboard this second boat, and his own, rather charred but not seriously damaged, was towed to shore.  Later the girls learned that there had been some gasoline which leaked from his tank.  He had been repairing his motor, which had stalled, when a spark from the electric wire set fire to the gasoline.  There was a slight explosion, followed by the fire.