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."