"In this case," added Whistler Morgan, "the sub may have wirelessed word
for supplies. We don't know how many alien enemies may be running
wireless stations in the United States. The Secret Service men are
unearthing them all the time."

"Well," sighed Ikey, "I only hope we'll catch up with this oil tub we're
hunting just as she is unloading her cargo onto a sub. Then! Blooey!
We'll drop a depth bomb or two, and settle Mr. Submarine."

"Just like _that_!" drawled Whistler. "It sounds easy. How many times
did the _Colodia_ chase a U-boat and lose it?"

"Crickey!" breathed Torry, "even the _Colodia_ couldn't travel like this
shark."

"Oh! you admit it, do you?" grinned Frenchy. "Well, we are going some!"

But there was an element working against the S. P. 888--an element which
could not be controlled. No matter how speedy the oil boat might have
been, the chaser could have overtaken her had she kept a straight
course. That was understood.

But the farther they went the more certain it was that this new element
was going to balk them. It was fog. The horizon was masked by it, and
soon the damp feel of it was upon them.

Mr. MacMasters paced the deck anxiously. Not a smudge of smoke did he or
the lookouts raise. But the growing fog cloud would soon have hidden
anything of the kind, even if the oil boat had been near at hand.