and he felt like expressing his feelings decidedly.

He was saved the trouble. The grimy stoker who had witnessed the
struggle and the fall appeared in the door of the engine-room. He saw
Frank and cried:

"Hello, you! So you're all right? Wonder you wasn't killed. You came
down with a rush, young feller, but you went back just as quick."

Frank understood instantly.

"Here is a man who saw it!" he cried. "He will tell you that I am not
lying."

The engineer turned to the stoker.

"How did he happen to fall?" he asked.

"He didn't fall," declared the begrimed coal heaver.

"No? What then--"

"'Nother chap jumped on his back and flung him down. It's wonderful he
wasn't killed."

Frank was triumphant. He regarded the engineer and his assistant with a
grim smile on his face.

"This is incredible!" exclaimed the engineer. "Who could have done such
a thing?"

"Somebody who came from this room!" rang out Merry's clear voice.

"This shall be investigated!" declared the engineer. "Look around! See
if you can find the man who attacked you. The only ones here are myself,
Mr. Gregory, and the wipers."

"I want a look at those wipers," said Frank.

"You shall have it. Mr. Gregory and I were talking together over here
all the time you were gone."

"Oh, I do not suspect you," said Merry; "but I want a good look at those
wipers."

"Did you see the man who threw you into the stoke-hole?"

"No, but--"

"Then how will you know who it was if you see him?"

"Whoever did so had a reason for the act--a motive. He must have known
me before. I may know him."

"Come," invited the engineer.

He called one of the wipers down from amid the sliding shafts and moving
machinery. The man came unhesitatingly.

Frank took a square look at this man, who did not seek to avoid
inspection.

"Never saw him before," confessed Merry.

The wiper was dismissed.

"Hackett," called the engineer.

The other wiper did not seem to hear. He pretended to be very busy, and
kept at work.

"Hackett!"

He could not fail to hear that. He kept his face turned away, but
answered:

"Yes, sir."

"Come here. I want you."

The wiper hesitated. Then he turned and slowly approached. His face was
besmeared till scarcely a bit of natural color showed, and his hat was
pulled low over his eyes. He shambled forward awkwardly, and stood in an
awkward position, with his eyes cast down.

Frank looked at him closely and started. Then, in a pe