d I knew now why she had worn a gas-mask.

This discovery gave me a horrid shock. I was brought down with a crash
from my high sentiment to something earthly and devilish. I was fairly
well used to Boche filthiness, but this seemed too grim a piece of the
utterly damnable. I wanted to have Ivery by the throat and force the
stuff into his body, and watch him decay slowly into the horror he had
contrived for honest men.

'Let's get out of this infernal place,' I said.

But Mary was not listening. She had picked up one of the newspapers and
was gloating over it. I looked and saw that it was open at an
advertisement of Weissmann's 'Deep-breathing' system.

'Oh, look, Dick,' she cried breathlessly.

The column of type had little dots made by a red pencil below certain
words.

'It's it,' she whispered, 'it's the cipher--I'm almost sure it's the
cipher!'

'Well, he'd be likely to know it if anyone did.'

'But don't you see it's the cipher which Chelius uses--the man in
Switzerland? Oh, I can't explain now, for it's very long, but I
think--I think--I have found out what we have all been wanting. Chelius
...'

'Whisht!' I said. 'What's that?'

There was a queer sound from the out-of-doors as if a sudden wind had
risen in the still night.

'It's only a car on the main road,' said Mary.

'How did you get in?' I asked.

'By the broken window in the next room. I cycled out here one morning,
and walked round the place and found the broken catch.'

'Perhaps it is left open on purpose. That may be the way M. Bommaerts
visits his country home ... Let's get off, Mary, for this place has a
curse on it. It deserves fire from heaven.'

I slipped the contents of the attache case into my pockets. 'I'm going
to drive you back,' I said. 'I've got a car out there.'

'Then you must take my bicycle and my servant too. He's an old friend
of yours--one Andrew Amos.'

'Now how on earth did Andrew get over here?'

'He's one of us,' said Mary, laughing at my surprise. 'A most useful
member of our party, at present disguised as an _infirmier_ in Lady
Manorwater's Hospital at Douvecourt. He is learning French, and ...'

'Hush!' I whispered. 'There's someone in the next room.'

I swept her behind a stack of furniture, with my eyes glued on a crack
of light below the door. The handle turned and the shadows raced before
a big electric lamp of the kind they have in stables. I could not see
the bearer, but I guessed it was the old wo