abruptly
to Colston--

"Das Wort ist Freiheit."

Arnold knew German enough to know that this meant "The word is
'Freedom,'" but why it should have been spoken in a foreign language
mystified him not a little.

While he was thinking about this the door opened, as if by a released
spring, and he saw before him a long, narrow passage, lit by four
electric arcs, and closed at the other end by a door, guarded by a
sentry armed with a magazine rifle.

He followed Colston down the passage, and when within a dozen feet of
the sentry, he brought his rifle to the "ready," and the following
strange dialogue ensued between him and Colston--

"Quien va?"

"Zwei Freunde der Bruderschaft."

"Por la libertad?"

"Fuer Freiheit ueber alles!"

"Pass, friends."

The rifle grounded as the words were spoken, and the sentry stepped
back to the wall of the passage.

At the same moment another bell rang beyond the door, and then the
door itself opened as the other had done.

They passed through, and it closed instantly behind them, leaving
them in total darkness.

Colston caught Arnold by the arm, and drew him towards him, saying as
he did so--

"What do you think of our system of passwords?"

"Pretty hard to get through unless one knew them, I should think. Why
the different languages?"

"To make assurance doubly sure every member of the Inner Circle must
be conversant with four European languages. On these the changes are
rung, and even I did not know what the two languages were to be
to-night before I entered the house, and if I had asked for 'Mr.
Brown' instead of 'Mr. Smith,' we should never have got beyond the
drawing-room.

"When the footman told me in German that the word was 'Freedom,' I
knew that I should have to answer the challenge of the sentry in
German. I did not know that he would challenge in Spanish, and if I
had not understood him, or had replied in any other language but
German, he would have shot us both down without saying another word,
and no one would ever have known what had become of us. You will be
exempt from this condition, because you will always come with me. I
am, in fact, responsible for you."

"H'm, there doesn't seem much chance of any one getting through on
false pretences," replied Arnold, with an irrepressible shudder. "Has
any one ever tried?"

"Yes, once. The two gentlemen whose disappearance made the famous
'Clapham Mystery' of about twelve months ago. They were two of the
s