Herr Stolberg," was Ray's bold reply.
"You'll find your clever wife tied up to a tree in the field opposite."

The younger man held a revolver, but from his face I saw that he was a
coward.

"What do you mean?" demanded the other.

"I mean that I intend destroying all this excellent espionage work of
yours. You've lived here for two years, and have been very busy
travelling in your car and gathering information. But," he said, "you
were a little unwise in putting upon your car the new Feldmarck
non-skids, the only set, I believe, yet in England. They may be very
good tyres, but scarcely adapted for spying purposes. I, for instance,
noticed the difference in the tracks the wheels made one evening when
you met your wife outside Metfield Park, and that is what led me to
you."

"You'd destroy all my notes and plans!" he gasped, with a fierce oath in
German. "You shall never do that--you English cur!"

"Then stand aside and watch!" he cried, withdrawing from the room on to
the landing. "See, look here!" and he opened his bag. This caused both
men to withdraw from the room to peer inside his bag.

With a quiet movement, however, Ray flung a small dark object into the
centre of the room, and in an instant there was a bright blood-red
flash, and the whole place was one mass of roaring flames, which,
belching from the door, caused us all to beat a hasty retreat. In a
moment the place was a furnace.

The spies shouted, cursed, and fired their revolvers at us through the
thick smoke, but we were quickly downstairs and out in the road.

"That will soon drive out the rats," laughed Ray, as we watched the
flames burst through the roof and saw the two men escape half dressed
through the window we had opened.

And as, with the red glare behind us, we hurried back to the spot where
we had left our car, Ray remarked, with a laugh of triumph:

"Stolberg bought that place two years ago with money, no doubt, supplied
from Berlin, so he's scarcely likely to come upon us for incendiarism, I
think. It was the only way--to make one big bonfire of the whole thing!"

CHAPTER IV

HOW THE GERMANS ARE PREPARING FOR INVASION

"We're going down to Maldon, in Essex," Ray Raymond explained as we
drove along in a taxi-cab to Liverpool Street Station late one grey
snowy afternoon soon after our return from Norfolk.

He had been away from London for three weeks, and I had no idea of his
whereabouts, except that one night he rang m