they exchanged stories. Harry told his first. Then he heard of Dick's
escape, and of his meeting with Jack. He nodded at the story they had heard
from Gaffer Hodge.

"That accounts for how Graves knew," he said, with much satisfaction. "What
happened then?"

When he heard of how they had thought too late of calling Colonel
Throckmorton by telephone he sighed.

"If you'd only got that message through before Graves got in his work!" he
said. "He'd have had to believe you then, of course. How unlucky!"

"I know," said Jack. "We were frightfully sorry. And then we went out to
find where the wire was cut, and they got Dick. But I got away, and I
managed to stay fairly close to them. I followed them when they left Dick
in a little stone house, as a prisoner, and I heard this--I heard them
talking about getting a big supply of petrol. Now what on earth do they
want petrol for? They said there would still be plenty left for the
automobiles--and then that they wouldn't need the cars any more, anyhow!
What on earth do you make of that, Harry?"

"Tell me the rest, then I'll tell you what I think," said Harry. "How did
you get Dick out? And did you hear them saying anything that sounded as if
it might be useful, Dick?"

"That was fine work!" he said, when he had heard a description of Dick's
rescue. "Jack, you seem to be around every time one of us gets into trouble
and needs help!"

Then Dick told of the things he had overheard--the mysterious references to
Von Wedel and to things that were to be done to the barracks at Ealing and
Houndsditch. Harry got out a pencil and paper then, and made a careful note
of every name that Dick mentioned. Then he took a paper from his pocket.

"Remember this, Dick?" he asked. "It's the thing I spoke of that I forgot
until I came across it in my pocket this morning."

"What is it, Harry?"

"Don't you remember that we watched them heliographing some messages, and
put down the Morse signs? Here they are. Now the thing to do is to see if
we can't work out the meaning of the code. If it's a code that uses words
for phrases we're probably stuck, but I think it's more likely to depend on
inversions."

"What do you mean, Harry?" asked Jack. "I'm sorry I don't know anything
about codes and ciphers."

"Why, there are two main sorts of codes, Jack, and, of course, thousands of
variations of each of those principal kinds. In one kind the idea is to
save words--in telegraphing or cabling. So th