"It was true. It changed him. He forgot me.... He told father he must strike at once--to-night.... It's going to be to-night. Somehow, by some means, he's going to do some awful thing. He rushed out.... Then Philip's wife came with a note ... and when father read it he ... died. It killed him...."
"To-night. Cantor is going to do something to-night. What? What else do you know?"
"Let me think. It was all so terrible.... He has an aeroplane. He is going to blow up factories and channels. In an hour. He said he could do it all in an hour."
"In his car. I don't know where he went--it was that way"--she pointed--"away from the city.... He said it would be easy, that there was no way to stop him."
Potter stood motionless, thinking as he had never thought before, sometimes thinking aloud.
"He has Matthews's 'plane," he said. "He'll use that--to drop explosives.... He's been gone hours. He can't be caught and stopped. Once he reaches that 'plane, there's no way to stop him. Even if the city was warned, he could do as he wished.... There's no way to stop him."
"But you must stop him.... If this thing is done it will be my fault--mine!... Because I didn't tell.... But now I've told.... Oh, Potter, you must do something.... I'm not a traitor.... I love my country. Don't let me be blamed for this. There's a way to prevent it--some way.... You must find it."
"If we knew where the 'plane was--or the explosive stored." He stopped suddenly, and a surge of joy welled up to his eyes. "I know," he said. "I know where he must start.... That island, Hildegarde, where we fell.... That's what the island was for. They made explosive, stored explosive.... There is where he will start."
He looked at his watch. "Nearly six," he said.
"He won't start for hours--until midnight. He'll be safest then.... Can't you get there in time?"
"I don't think a motor-boat could reach that island--the ice in the lake."
"_He's_ got to reach it. _He_ can reach it."
"He'll have that 'plane hidden on the lake shore. He'll fly across and take on his explosives."
"You have an aeroplane, too," she said, simply.
It was a thought brightly gleaming in the darkness; it was a thought which fitted that man and girl like a garment skilfully made. It called to them and beckoned with its recklessness, the adventure of it, its audacity, its quality of knight-errantry. To be a knightly champion of his country, riding a steed of the air in the lists of the heavens! That was indeed an enterprise in tune with the soul of Potter Waite, in tune with the not less turbulent soul of Hildegarde von Essen.