“I don’t know,” was the reply.  “Just before the explosion the three of us entered an automobile together, and then as we were starting away I remembered something which made it necessary for me to reenter the house.  When I came out again, just a few seconds before the explosion, the prince and Miss Thorne had gone.”

The secretary’s lips curled down in disapproval.

“Wasn’t it rather unusual, to put it mildly, to leave your prisoners to their own devices that way?” he asked.

“Well, yes,” Mr. Grimm admitted.  “But the circumstances were unusual.  When I entered the house I had locked a man in the cellar.  I had to go back to save his life, otherwise—­”

“Oh, the guard at the door, you mean?” came the interruption.  “Who was it?”

Mr. Grimm glanced at his chief, who nodded.

“It was Mr. Charles Winthrop Rankin of the German embassy,” said the young man.

“Mr. Rankin of the German embassy was on guard at the door?” demanded the president quickly.

“Yes.  We got out safely.”

“And that means that Germany was—!”

The president paused and startled glances passed around the table.  After a moment of deep abstraction the secretary went on: 

“So Miss Thorne and the prince escaped.  Are they still in this country?”

“That I don’t know,” replied Mr. Grimm.  He stood silent a moment, staring at the president.  Some subtle change crept into the listless eyes, and his lips were set.  “Perhaps I had better explain here that the personal equation enters largely into an affair of this kind,” he said at last, slowly.  “It happens that it entered into this.  Unless I am ordered to pursue the matter further I think it would be best for all concerned to accept the fact of Miss Thorne’s escape, and—­” He stopped.

There was a long, thoughtful silence.  Every man in the room was studying Mr. Grimm’s impassive face.

“Personal equation,” mused the president.  “Just how, Mr. Grimm, does the personal equation enter into the affair?”

The young man’s lips closed tightly, and then: 

“There are some people, Mr. President, whom we meet frankly as enemies, and we deal with them accordingly; and there are others who oppose us and yet are not enemies.  It is merely that our paths of duty cross.  We may have the greatest respect for them and they for us, but purposes are unalterably different.  In other words there is a personal enmity and a political enmity.  You, for instance, might be a close personal friend of the man whom you defeated for president.  There might”—­he stopped suddenly.

“Go on,” urged the president.

“I think every man meets once in his life an individual with whom he would like to reckon personally,” the young man continued.  “That reckoning may not be a severe one; it may be less severe than the law would provide; but it would be a personal reckoning.  There is one individual in this affair with whom I should like to reckon, hence the personal equation enters very largely into the case.”