“You know,” he said at last, “the old idea of the forteresse mobile?

“Yes.”

He couldn’t tell whether Drayton was going to be interested or not.  He rather thought he wasn’t.

“It hasn’t come to anything, has it?”

Drayton smiled and his eyes glittered.  He knew what that excited gleam in Drayton’s eyes meant.

“No,” he said.  “Not yet.”

And Nicky had an awful premonition of his doom.

“Well,” he said, “I believe there’s something in it.”

“So do I, Nicky.”

Drayton went on.  “I believe there’s so much in it that—­Look here, I don’t know what put it into your head, and I’m not asking, but that idea’s a dead secret.  For God’s sake don’t talk about it.  You mustn’t breathe it, or it’ll get into the air.  And if it does my five years’ work goes for nothing.  Besides we don’t want Germany to collar it.”

And then:  “Don’t look so scared, old chap.  I was going to tell you about it when I’d got the plans drawn.”

He told him about it then and there.

“Low on the ground like a racing-car—­”

“Yes,” said Nicky.

“Revolving turret for the guns—­no higher than that—­”

“Yes,” said Nicky.

“Sort of armoured train.  Only it mustn’t run on rails.  It’s got to go everywhere, through anything, over anything, if it goes at all.  It must turn in its own length.  It must wade and burrow and climb, Nicky.  It must have caterpillar wheels—­”

“By Jove, of course it must,” said Nicky, as if the idea had struck him for the first time.

“What have you got there?” said Drayton finally as Nicky rose and picked up his dispatch-box.  “Anything interesting?

“No,” said Nicky.  “Mostly estimates.”

For a long time afterwards he loathed the fields between Eltham and Kidbrooke, and the Mid-Kent line, and Charing Cross Station.  He felt as a man feels when the woman he loves goes from him to another man.  His idea had gone from him to Drayton.

And that, he said to himself, was just like his luck, just like the jolly sells that happened to him when he was a kid.

To be sure, there was such a thing as sharing.  He had only to produce his plans and his finished model, and he and Drayton would go partners in the Moving Fortress.  There was no reason why he shouldn’t do it.  Drayton had not even drawn his plans yet; he hadn’t thought out the mechanical details.

He thought, “I could go back now and tell him.”

But he did not go back.  He knew that he would never tell him.  If Drayton asked him to help him with the details he would work them out all over again with him; but he would never show his own finished plans or his own model.

He didn’t know whether it had been hard or easy for him to give up the Moving Fortress.  He did it instinctively.  There was—­unless he had chosen to be a blackguard—­nothing else for him to do.