memory doesn't fail me, the gas escapes from the earth, and in some
districts--particularly in Baku--it has actually been burning for years
as sacred fires. A question of atmosphere and education, you see, Sir
Nigel."

"Good Heavens! Then you mean to say that those beastly things out there
are not lit by any human or superhuman agency at all!" exploded Merriton
at this juncture. "And that they have nothing whatever to do with the
vanishing of Wynne and Collins?"

Cleek shook his head emphatically.

"Pardon me," he said, "but I didn't say that. The first part of the
sentence I agree with entirely. Those so-called flames are lit only by
the hand of the Infinite. And the Infinite is always mysterious, Sir
Nigel. But as to whether they have any bearing upon the disappearances of
those two men is a horse of another colour. We'll look into that later
on. In coal-mines marsh gas is considered highly dangerous, and the
miners call it fire-damp. But that is by the way. What enters into the
immediate question is the fact that there is a patch of charred grass
upon the Fens where you say the vanished man, Dacre Wynne's footprints
suddenly ended. Hmm."

He stopped speaking suddenly, and getting up again crossed over to the
window. He stood for a moment looking out of it, his brows drawn down,
his face set in the stern lines that betokened concentration of thought.

Mr. Narkom and Merriton watched him with something of wonder in their
eyes. To Merriton, at any rate, who really knew so little of Cleek's
unique and powerful mind, the fact of a policeman having such extensive
information was surprising in the extreme.

"You don't think, then," he said, breaking the silence that had fallen
upon them, "that this--er--marsh gas could have caused the death of Wynne
and Collins? Burnt 'em alive, so to speak?"

Cleek did not move at this question. They merely saw his shoulders twitch
as though he didn't wish to be bothered at the moment.

"Don't know," he said laconically, "and if that were true, where are
the bodies?... Gad! Just as I thought! Come here, gentlemen, this may
interest you. See that flame there! It's no more natural marsh gas than
I am! There's human agency all right, Sir Nigel. There's natural marsh
gas and there are--other things as well. Those marsh lights are being
augmented. But for what purpose? What reason? That's the thing we've got
to find out."

CHAPTER XII

"AS A THIEF IN THE NIGHT--"

The arri