a possible--only possible, mark you--story, based on the
supposition that my badge theory is correct. A German who speaks
English perfectly is given a nice warm uniform taken from a captured
British officer. Then he is told to go over to the British lines and
see what he can find out. He comes one night; perfectly easy; no
trouble; until walking along the front line he meets another
officer--alone: an officer of the same regiment as that whose uniform
he is wearing. Unavoidable; in fact, less likely to raise suspicion
with the frequent changes that occur if he goes to the same regiment
than if he went to another. But something happens: either the other
officer's suspicions are aroused, or the German does not wish to be
recognised again by him. The trench is quiet; an occasional rifle is
going off, so he does the bold thing. He shoots him from point-blank
range--probably with a Colt. As he stands there with the dead officer
in front of him, waiting, listening hard, wondering if he has been
heard, he sees the two badges on the officer's coat. So, being a cool
hand, he takes off the left one, puts it on his own coat, and
disappears for a time. Quite easy; especially when the trenches are
old German ones."

"Really, Major, you seem to have made a speciality of detective
fiction. As you said, I suppose your theory is possible."

Jesson spoke casually, but his eyes for the first time left the face of
the man opposite him and roved towards the door. For the first time a
sudden ghastly suspicion of the truth entered the Sapper's brain; and
even as it did so he noticed that Staunton's revolver--the cleansing
finished--pointed steadily at Jesson's chest.

"I am glad you think it possible. To render it probable we must go a
bit farther. The essence of all detective stories is the final clue
that catches the criminal, isn't it?" The revolver moved an inch or
two farther into prominence.

"Good Lord, Dickie? Is that gun of yours loaded?" cried the Adjutant
in alarm. For the first time he also seemed to become aware that
something unusual was happening, and he suddenly stood up. "What the
devil is it, Major? What have you got that gun on him for?"

"For fun, dear boy, for fun. It's part of the atmosphere. We've got
to the point haven't we, where--in my story, of course--the German
dressed in Brinton's uniform comes into the English lines. Now what
sort of a man would they send in this part of the line, wher