t closet. Before I could utter a word I was a prisoner
behind a locked door. I called several times, and, receiving no
response, realized that I must be some distance from anyone else and
that the noises of the engines completely drowned out my voice.

"Every moment it became more stifling in there, and I had no doubt that
I had walked directly into a death-trap. It was then I began signaling
on the steam-pipe. I guess it was a mighty lucky thing for me that Slim
Goodwin strolled out on deck just at the time he did."

And that was all that Lieutenant Mackinson could tell. The mysterious
stranger remained what he had been from the first--a desperate and
dangerous and unknown spy, lurking somewhere upon the American transport
_Everett_ with the evident intention of making the ship's position known
to German U-boats when the _Everett_ and her convoy of cruisers and
destroyers entered the danger zone.

Then it was, with the lieutenant temporarily disabled as a result of his
experience, that the three boys from Brighton, who seemed somehow to
have been selected by Fate as the despoilers of all the spy's plans, put
their heads together to devise a scheme of capture.

"We've got more than one good reason for wanting to get this fellow,"
Slim reminded the others with considerable warmth, during the course of
their deliberations. "First and foremost, of course, is our plain duty
to our country, to which he is an enemy and a traitor.

"But, in addition to that, there is that knockout that he handed to Joe,
and the midnight scare he gave Jerry and me, and finally his effort to
kill Lieutenant Mackinson by slow suffocation, not to mention the nerve
of the fellow in coming back the way he has."

"Yes," added Jerry, "we owe him a lot, and it is up to us to figure out
how we can square the debt."

"Well," said Joe, "I think I've got a plan that will work; but we've got
to remember that we are dealing with a very shrewd man."

"Well, what's your suggestion?" Slim demanded.

"That we divide our forces," answered Joe solemnly, "lie in wait and try
to ambush the foe."

"Right!" cried Jerry. "Joe, you'll be a general before this war's over."

"Along what lines do we disperse our forces, General?" asked Slim.

"Along what lines would His Royal Stoutness suggest?" demanded Jerry.

"Oh, you don't have to keep reminding me that I'm a trifle heavy," Slim
replied in a peevish tone.

"A trifle heavy! Get that, will you," echoed Jer