“My dear fellow,” he said, “you would have been maimed or killed.  You do not seem to be harmed.”

Frank realized that the engineer actually doubted his word.

“He might have fallen,” said the assistant; “but it would have broken his neck.”

“I tell you I was attacked from behind and thrown down!” exclaimed Frank.  “I managed to get hold of the ladder and slide, so I was not killed.”

The engineer looked annoyed.

“This is what comes of letting a passenger in here,” he said.  “It’s the last time I’ll do it on my own responsibility.  Now if you go out and tell you were thrown into the stoke-hole, there’ll be any amount of fuss over it.”

“I am telling it right here,” said Frank, grimly, “and I want to know who did the trick.  Somebody who came from this room must have done it.”

“Impossible!”

“Then where did he come from?”

The engineer and his assistant looked at each other, and the former began to swear.

“What do you think of it, Joe?” he asked.

“Think you made a mistake, Bill; but his story won’t go.  Nobody’ll take any stock in it.”

Frank was angry.  It was something unusual for his word to be doubted, 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.”