The prince glanced again at his watch, then thoughtfully weighed the percussion cap in his hand, after which, with a curious laugh, he walked over to the squat iron globe in an opposite corner of the room.  He bent over it half a minute, then straightened up.

“That cap, Mr. Grimm, has one disadvantage,” he remarked casually.  “When it is attached to a mine or torpedo it can not be disconnected without firing it.  It is attached.”  He turned to the others.  “It is needless to discuss the matter further just now.  If you will follow me?  We will leave Mr. Grimm here.”

With a strange little cry, neither anger nor anguish, yet oddly partaking of the quality of each, Isabel went quickly to the prince.

“How dare you do such a thing?” she demanded fiercely.  “It is murder.”

“This is not a time, Miss Thorne, for your interference,” replied the prince coldly.  “It has all passed beyond the point where the feelings of any one person, even the feelings of the woman who has engineered the compact, can be considered.  A single life can not be permitted to stand in the way of the consummation of this world project.  Mr. Grimm alive means the compact would be useless, if not impossible; Mr. Grimm dead means the fruition of all our plans and hopes.  You have done your duty and you have done it well; but now your authority ends, and I, the special envoy of—­”

“Just a moment, please,” Mr. Grimm interrupted courteously.  “As I understand it, your Highness, the mine there in the corner is charged?”

“Yes.  It just happened to be here for purposes of experiment.”

“The cap is attached?”

“Quite right.”  The prince laughed.

“And at three o’clock, by your watch, the mine will be fired by a wireless operator fifteen miles from here?”

“Something like that; yes, very much like that,” assented the prince.

“Thank you.  I merely wanted to understand it.”  Mr. Grimm pulled a chair up against the door and sat down, crossing his legs.  On his knees rested the barrel of a revolver, glittering, fascinating, in the semi-darkness.  “Now, gentlemen,” and he glanced at his watch, “it’s twenty-one minutes of three o’clock.  At three that mine will explode.  We will all be in the room when it happens, unless his Highness sees fit to destroy the compact.”

Eyes sought eyes, and the prince removed his mask with a sudden gesture.  His face was bloodless.

“If any man,” and Mr. Grimm gave Miss Thorne a quick glance, “I should say, any person, attempts to leave this room I know he will die; and there’s a bare chance that the percussion cap will fail to work.  I can account for six of you, if there is a rush.”

“But, man, if that mine explodes we shall all be killed—­blown to pieces!” burst from one of the cowled figures.

“If the percussion cap works,” supplemented Mr. Grimm.

Mingled emotions struggled in the flushed face of Isabel as she studied Mr. Grimm’s impassive countenance.