care. He walked three miles out of town and to the banks of the
Paraguay. There he carefully saturated the pages of both books in
water, carefully keeping the bindings from being wetted. Then he tore
one book to pieces, saving the leaves and inserting them between the
leaves of the other book. Then, with a brazil nut candle for
illumination, he began to write.

* * * * *

You see, when two thoroughly wetted pieces of paper are placed one above
the other with a hard surface such as the cover of another book under
them, you can write upon the top one with a stick. The writing will show
dark against the gray of the saturated paper. You then remove the top
sheet and end the writing reproduced on the bottom sheet. And then you
can dry the second sheet and find the marking vanished--until it is
wetted again. It is, in fact, a method of water-marking paper. And it is
the simplest of all methods of invisible writing.

Bell wrote grimly for hours. The book he had chosen was an old one, an
ancient copy of one of Lope de Vega's plays, and the pages were wrinkled
and yellow from age alone. When, by dawn, the last page was dried out,
there was no sign that anything other than antiquity had affected the
paper. And Bell wrapped it carefully, and addressed it to an elderly
senora of literary tastes in San Juan, Porto Rico, and enclosed an
affectionate letter to his very dear aunt, and signed it with an
entirely improbable name.

It was mailed before sunrise, the necessary stamps having been filched
from the burglarized bookstore and the price thereof being carefully
inserted in the till. Bell had made a complete and painstaking report of
every fact he had himself come upon in the matter of The Master and his
slaves and appended to it a copy of the report of the dead Secret
Service operative Number One-Fourteen. He destroyed that after copying
it. And he concluded that since he had been given dismissal by Jamison
in Rio, he considered himself at liberty to take whatever steps he saw
fit. And since the Senhorina Paula Canalejas had been kidnapped by
agents of The Master, he intended to take steps which might possibly
bring about her safety, but would almost certainly cause his death.

The report should at least be of assistance if the Trade set to work to
combat The Master. Bell had no information whatever about that still
mysterious and still more horrible person himself. But what he knew
about The M