"Are there any killed?" asked Tom, stopping the car near the
officer.

"I guess so--yes. And some of the houses are catching. Git back
now! You, too, with that car! You'll have to back up!"

"I've got to go through!" replied Tom, with tightening lips.
"I've got to go through, Cassidy!" He knew the officer, and the
latter now seemed, for the first time, to recognize the young
inventor.

"Oh, it's you, is it, Mr. Swift?" he exclaimed. "Well, go
ahead. But be careful. 'Tis dangerous there--very dangerous,
an'--"

His voice was lost in the roar of another explosion, not as
loud or severe as the first, but more plainly felt by Tom and
Ned, for they were nearer to it.

"Now will you git back!" cried Policeman Cassidy, and the crowd
did, without further urging.

Tom started the runabout forward again.

"We've got to rescue Mary!" he said to Ned, who nodded.

In another moment the two young men were lost to sight in a
swirl of smoke that swept across the street. And while they are
thus temporarily hidden may not this opportunity be taken of
telling new readers something of the hero of this story?