A Curious Experience by Mark Twain

We sat with closed doors, and instructed the guard outside to allow no interruption.
First we opened the letter captured at the stable.
It read as follows:
-- "HOLY ALLIANCE, -- Found, in the usual gun, commands from the Master, left there last night,
which set aside the instructions heretofore received from the subordinate quarter. Have left in the gun the usual indication that the commands reached the proper hand--"
Webb, interrupting: `Is n`t the boy under constant surveillance now؟"
I said yes; he had been under strict surveillance ever since the capturing of his former letter.
"Then how could he put anything into a gun, or take anything out of it, and not get caught؟"
"Well," I said, "I don`t like the look of that very well."
"I don`t, either,"said Webb.
"It simply means that there are conspirators among the very sentinels. Without their connivance in some way or other, the thing could n`t have been done."