“A desperate enterprise is on foot，that is plain enough.To-night is the time set for it—that，also，is plain.The exact nature of the enterprise—I mean the manner of it—is hidden away under those blind bunches of M's and F's，but the end and aim，I judge，is the surprise and capture of the post.We must move quick and sharp now.I think nothing can be gained by continuing our clandestine policy as regards Wicklow.We must know，and as soon as possible，too，where ‘166'is located，so that we can make a descent upon the gang there at 2a.m.and doubtless the quickest way to get that information will be to force it out of that boy.But first of all，and before we make any important move，I must lay the facts before the War Department，and ask for plenary powers.”
The despatch was prepared in cipher to go over the wires；I read it，approved it，and sent it along.
We presently finished discussing the letter which was under consideration，and then opened the one which had been snatched from the lame gentleman.It contained nothing but a couple of perfectly blank sheets of note-paper!It was a chilly check to our hot eagerness and expectancy.We felt as blank as the paper，for a moment，and twice as foolish.But it was for a moment only；for，of course，we immediately afterward thought of “sympathetic ink.”We held the paper close to the fire and watched for the characters to come out，under the influence of the heat；but nothing appeared but some faint tracings，which we could make nothing of.We then called in the surgeon，and sent him off with orders to apply every test he was acquainted with till he got the right one，and report the contents of the letter to me the instant he brought them to the surface.This check was a confounded annoyance，and we naturally chafed under the delay；for we had fully expected to get out of that letter some of the most important secrets of the plot.
Now appeared Sergeant Rayburn，and drew from his pocket a piece of twine string about a foot long，with three knots tied in it，and held it up.
“I got it out of a gun on the water-front，”said he.“I took the tompions out of all the guns and examined close；this string was the only thing that was in any gun.”
So this bit of string was Wicklow's “sign”to signify that the “Master's”commands had not miscarried.I ordered that every sentinel who had served near that gun during the past twenty-four hours be put in confinement at once and separately，and not allowed to communicate with any one without my privity and consent.
A telegram now came from the Secretary of War.It read as follows:
Suspend habeas corpus.Put town under martial law.
Make necessary arrests.Act with vigor and promptness.
Keep the department informed.
We were now in shape to go to work.I sent out and had the lame gentleman quietly arrested and as quietly brought into the fort；I placed him under guard，and forbade speech to him or from him.He was inclined to bluster at first，but he soon dropped that.
Next came word that Wicklow had been seen to give something to a couple of our new recruits；and that，as soon as his back was turned，these had been seized and confined.Upon each was found a small bit of paper，bearing these words and signs in pencil:
In accordance with instructions，I telegraphed to the Department，in cipher，the progress made，and also described the above ticket.We seemed to be in a strong enough position now to venture to throw off the mask as regarded Wicklow；so I sent for him.I also sent for and received back the letter written in sympathetic ink，the surgeon accompanying it with the information that thus far it had resisted his tests，but that there were others he could apply when I should be ready for him to do so.
Presently Wicklow entered.He had a somewhat worn and anxious look，but he was composed and easy，and if he suspected anything it did not appear in his face or manner.I allowed him to stand there a moment or two;then I said，pleasantly：
“My boy，why do you go to that old stable so much？”
He answered，with simple demeanor and without embarrassment：
“Well，I hardly know，sir；there isn't any particular reason，except that I like to be alone，and I amuse myself there.”
“You amuse yourself there，do you？”
“Yes，sir，”he replied，as innocently and simply as before.
“Is that all you do there？”
“Yes，sir，”he said，looking up with childlike wonderment in his big,soft eyes.
“You are sure？”
“Yes，sir，sure.”
After a pause I said：
“Wicklow，why do you write so much？”
“I？I do not write much，sir.”
“You don't？”
“No，sir.Oh，if you mean scribbling，I do scribble some，for amusement.”
“What do you do with your scribblings？”
“Nothing，sir—throw them away.”
“Never send them to anybody？”
“No，sir.”
I suddenly thrust before him the letter to the “Colonel.”He started slightly，but immediately composed himself.A slight tinge spread itself over his cheek.
“How came you to send this piece of scribbling，then？”
“I nev—never meant any harm，sir!”
“Never meant any harm!You betray the armament and condition of the post，and mean no harm by it？”
He hung his head and was silent.
“Come，speak up，and stop lying.Whom was this letter intended for？”
He showed signs of distress now；but quickly collected himself，and replied，in a tone of deep earnestness：
“I will tell you the truth，sir—the whole truth.The letter was never intended for anybody at all.I wrote it only to amuse myself.I see the error and foolishness of it now;but it is the only offense，sir，upon my honor.”
“Ah，I am glad of that.It is dangerous to be writing such letters.I hope you are sure this is the only one you wrote？”
“Yes，sir，perfectly sure.”
His hardihood was stupefying.He told that lie with as sincere a countenance as any creature ever wore.I waited a moment to soothe down my rising temper，and then said：
“Wicklow，jog your memory now，and see if you can help me with two or three little matters which I wish to inquire about.”
“I will do my very best，sir.”
“Then，to begin with—who is ‘the Master'？”