rushed some of the black
powder over it, blowing off the surplus. To the satisfaction of both
men, there showed up near the left bottom corner the distinct mark of a
left thumb.

"Now the other side."

Willis turned the paper and repeated the operation on the back. There he
got prints of a left fore and second finger.

"Excellent, clear prints, those," Willis commented, continuing: "And now
I have something to tell you. While you were away I have been thinking
over this thing, and I believe I've got an idea."

Laroche looked interested, and the other went on slowly:

"There are two brandy-carrying lorries. Every night one of these lies
at the distillery and the other at the clearing; one is being loaded and
the other unloaded; and every day the two change places. Now we may take
it that neither of those lorries is sent to any other place in the town,
lest the brandy tanks might be discovered. For the same reason, they
probably only make the one run mentioned per day. Is that right so far?"

"I should think so," Laroche replied cautiously.

"Very well. Let us suppose these two lorries are Nos. 1 and 2. No.
1 goes to the distillery say every Monday, Wednesday and Friday, and
returns on the other three days, while No. 2 does vice versa, one trip
each day remember. And this goes on day after day, week after week,
month after month. Now is it too much to assume that sooner or later
someone is bound to notice this--some worker at the clearing or
the distillery, some policeman on his beat, some clerk at a window
over-looking the route? And if anyone notices it will he not wonder why
it always happens that these two lorries go to this one place and to no
other, while the syndicate has six lorries altogether trading into the
town? And if this observer should mention his discovery to someone
who could put two and two together, suspicion might be aroused,
investigation undertaken, and presently the syndicate is up a tree. Now
do you see what I'm getting at?"

Laroche had been listening eagerly, and now he made a sudden gesture.

"But of course!" he cried delightedly. "The changing of the numbers!"

"The changing of the numbers," Willis repeated. "At least, it looks like
that to me. No. 1 does the Monday run to the distillery. They change the
number plate, and No. 4 does it on Wednesday, while No. 1 runs to some
other establishment, where it can be freely examined by anyone who is
interested. How does it strike you?"