"Well, I think it's the man you call Prince Michael," observed Mr. Fisher, airily. "In fact, I'm sure it is. I've seen the police portraits of him." There was a dead silence, and Sir Walter's usually steady brain seemed to go round like a windmill. "But, hang it all!" he said at last, "even supposing his own explosion could have thrown him half a mile away, without passing through any of the windows, and left him alive enough for a country walk--even then, why the devil should he walk in this direction? The murderer does not generally revisit the scene of his crime so rapidly as all that." "He doesn't know yet that it is the scene of his crime," answered Horne Fisher. "What on earth do you mean? You credit him with rather singular absence of mind." "Well, the truth is, it isn't the scene of his crime," said Fisher, and went and looked out of the window. There was another silence, and then Sir Walter said, quietly: "What sort of notion have you really got in your head, Fisher? Have you developed a new theory about how this fellow escaped out of the ring round him?" "He never escaped at all," answered the man at the window, without turning round. "He never escaped out of the ring because he was never inside the ring. He was not in this tower at all, at least not when we were surrounding it." He turned and leaned back against the window, but, in spite of his usual listless manner, they almost fancied that the face in shadow was a little pale. "I began to guess something of the sort when we were some way from the tower," he said. "Did you notice that sort of flash or flicker the candle gave before it was extinguished? I was almost certain it was only the last leap the flame gives when a candle burns itself out. And then I came into this room and I saw that." He pointed at the table and Sir Walter caught his breath with a sort of curse at his own blindness. For the candle in the candlestick had obviously burned itself away to nothing and left him, mentally, at least, very completely in the dark. "Then there is a sort of mathematical question," went on Fisher, leaning back in his limp way and looking up at the bare walls, as if tracing imaginary diagrams there. "It's not so easy for a man in the third angle to face the other two at the same moment, especially if they are at the base of an isosceles. I am sorry if it sounds like a lecture on geometry, but--" "I'm afraid we have no time for it," said Wilson, coldly. "If this man is really coming back, I must give my orders at once." "I think I'll go on with it, though," observed Fisher, staring at the roof with insolent serenity. "I must ask you, Mr. Fisher, to let me conduct my inquiry on my own lines," said Wilson, firmly. "I am the officer in charge now." "Yes," remarked Horne Fisher, softly, but with an accent that somehow chilled the hearer. "Yes. But why?"