elp us?"

"First, I'd like to hear your explanations," stated the newcomer. "But
before you start your story, please tell me why you call me Mackinder."

"Isn't that your name?" asked Jimmie. "Tell us that!"

"Yes, that's my name, you know!" replied the stranger, smilingly. "But
how did you happen to know it? I'm rather puzzled, you know!"

"Why, you told us yourself on the train running into Amsterdam!" stated
Jimmie, with rising indignation. "Then we called you by that name while
you were trying to delay our start. Also Captain von Kluck used that name
when he referred to you. I guess it's your name all right!"

"I don't deny that!" stated the newcomer. "What puzzles me is how you
chaps know it so quickly, don't you know."

"It don't make much difference how we know the name so quickly," went on
Jimmie. "We'd know you anywhere we saw you. We'd especially recognize
that hand with the scar! That's a dead giveaway!"

The newcomer glanced quickly at his right hand, which Jimmie had
indicated. As he brought it up to view, the boys could see a jagged scar
running clear across the back. They had seen such a scar before.

With an accusing finger pointing at the disfigurement, Jimmie snapped out
in crisp accents that indicated plainly his excitement:

"That's the same hand that tied and gagged me in the warehouse in
Amsterdam, and the same hand that I saw shoved into the window of the
frontier hut to get the 'U-13' package. Deny it if you can!"

"I am not going to deny anything, you know!" returned the other coolly.
"You seem so positive about it there's little use denying!"

"You bet there's no use denying anything like that!" declared Jimmie with
some heat. "You can't deny that you tried to sic the German torpedo boat
destroyer onto us, either. You can't deny that you sneaked away from this
very submarine when I was painting the name on the bow. You'd better not
try to deny that you showed us to the British gunboat a while ago and got
them to fire at us. If you start denying anything," the boy went on, "I'm
going to deny that I'm neutral!"

With a laugh the newcomer threw back his head in amused fashion.

"Have your own way about it, you know," he replied, "but I'm going to
tell you one thing. I'm not Mackinder!"

CHAPTER XX

A MYSTERIOUS CRAFT

The surprise of the lads at this declaration of their visitor was
profound. They stared at the stranger who bore such a striking
resemblance to Mackinder an