“I was alone, alone,” Hildegarde said, tremulously, “and I was afraid.”

“The house is dark,” he said, peering about him. “I could make nobody hear—until you came. Where are the lights?”

“Lights!... I was afraid in the dark, but I dared not light a light.... It would have been awful to light a light.”

“What do you mean? Where are the servants?”

“I don’t know.... Gone.... Let me touch you. Let me feel your arm.... Come, it’s in here.”

He felt her pressing against him, sensed the shuddering of her body as she led him into the library. “There,” she whispered. “On the floor.... There....”

He saw something there, blackly outlined, something that sprawled grotesquely, offensively, something that sprawled motionless and horrible. Again he felt the rising of his hair and the chill of dread, and hesitated. Then he forced himself to step forward, to bend over that sprawling black thing, to light a match. As it flamed Hildegarde uttered a faint scream.

The tiny flame threw a fitful, distorting light on the man that lay there; made his features grotesque, appalling. The bulging, staring eyes seemed to be fastened upon Potter’s eyes.

“God!...” he exclaimed. “Your father!”

“My father,” she repeated.

“You were alone with that? Alone in the dark?”

“It was awful!” she whispered.

“He is dead.”

“Dead.”

“Who—who killed him?” Somehow he dreaded to ask that question.

“God!” she said, simply.

He stood up, grasped her shoulders with firm hands. “Pull yourself together,” he said, harshly. “Don’t go to pieces. What has happened? What does this mean?”

“I’m not going to pieces. I’m calm—but I’m frightened.”

Potter switched on the lights and bent over von Essen, examining him to find what had struck him down.

“There is no wound,” he said, lifting his face. “How did he die?”

“Because,” she said, quietly, “one of us had to die. God chose him.”

He fancied he caught a note of joy in her voice; it startled him, repelled him, so unnatural did it seem.

“Such a father,” she went on with unnatural calm. “His blood was my blood—but I hated him. His touch, the air he breathed, was defilement. I could not have borne it another day.... He had to die.”

“Hildegarde!”

“You think I’m heartless. You think I ought to cry.... Oh, I could sing! I’m free at last. Free of him, free of his defilement. If I could only get his blood out of my veins....”

“What are you saying? What has been going on here? Tell me.”

“He was a spy and a traitor and a murderer.... I discovered it. I knew it—and I couldn’t denounce him. He was my father, don’t you see? My father!... You can’t betray your father to the police. I hated him for it, and I loved my country—but I couldn’t denounce him.”

“Your father a spy? A German agent?”

“Yes.”

This explained much. He fell silent, striving to comprehend something of the tortures she had endured, striving to picture the life she must have led. “You poor child!” he said, softly.

“When you came with questions—I couldn’t answer. You called me a traitor ... and I dared not tell you. He was my father and—and I couldn’t have lived to have people point to me and call me the daughter of a traitor. Could you have borne that?”

“No,” he said. “No.”

“He knew I had discovered what he was.... He locked me in. I’ve been watched day and night. I’ve been a prisoner.”

“Cantor?...”

“Was a guard. I couldn’t explain that.... He wanted me to marry him—to go with him without marriage—and father tried to force me.... He was trying to force me to-day.... And he died.” Suddenly she clutched his arm. “Oh,” she cried, “be quick! Do something!... They were warned!... I did it. I called Cantor Adolf von Arnheim. I had to do something to protect myself....”

“What did he say? Was it true?”

“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.”

“Where is Cantor? Where did he go?”

“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.”

“That way? Toward the lake?”

“Yes.”

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.”

“What time is it?”

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.

“Thank you,” he said, presently, his voice vibrant. “It’s worth a try.... I’m sorry,” he said, slowly, “that I didn’t know, didn’t understand. I must have hurt you. I wouldn’t have hurt you for worlds.... Last night I called you a traitor. If saying I am sorry—”

“How could you know?”

“If only the rest—that other thing—were a lie, too.” He ground his teeth, turned from her suddenly. “Good-by,” he said.

“Where are you going?”

“To get my ’plane ready.”

“And me? Are you going to leave me here alone—with him?” She motioned toward Herman von Essen. “Oh, you mustn’t!... I can’t stay! Take me with you.”

“No,” he said, “you can’t stay here.... Where can I take you? Minutes are precious.”

“Anywhere—away from here.... I don’t care. Don’t waste time with me.... Let me go with you—to the hangar. I’ll be all right there.”

“Get your wraps.”

She ran out of the room and up the stairs. As she opened her wardrobe door she hesitated an instant—there was only an instant of doubt. Then, quickly, deftly, wasting not a second, she removed her cumbering skirts and clad herself in those riding-breeches which she had worn that day so long ago—the day when she had stamped herself on Potter’s heart as a fairy prince.... She knew what she purposed.... Next she donned a fur-lined coat and driving-cap that covered her ears. She was not calm now, but she was very eager. A tinge of pink appeared in her pallid cheeks. By a little the weight of horror was shifted from her heart, shifted by hope.

Perhaps she was a trifle hysterical; perhaps the long strain with its sudden tragic climax had tried her until she could not see clearly, think straight from cause to effect. But hope had dawned, a hope that, perhaps, has dawned in the hearts of many whose guilt was more real than hers. She had seen a vision. In that vision she had bought herself free—free from guilt and free from defilement.

She descended to Potter. He turned low the light in the library, leaving Herman von Essen where he lay. Hildegarde stood in the door an instant, looking down at the thing that had been her father, drew a deep, gulping breath, and, covering her face, suffered Potter to lead her away.

Neither spoke as the car sped them to the hangar. It was dark, unoccupied. Potter unlocked the door and threw it open for Hildegarde to enter. In an instant he found the switch and turned on the lights.... Before them brooded Potter’s newest aeroplane, wings spread as though something found shelter beneath them. Hildegarde spoke of that. “Like a mother chicken,” she said, pointing, “protecting her brood.... What a brood she is protecting to-night!”

“You must help,” he said, sharply. “Throw off your coat.”

She did so, stood revealed as she had stood revealed that other day, that bountiful spring day. Potter shut his eyes. “Why?” he said, “why—”

She did not answer, and he stood, eyes open now, staring at her. His lips were white, straight, compressed. His throat ached.... How could that thing be true which she had confessed?... Every line of her proclaimed it a lie. The slenderness, the grace, the piquancy and boyish beauty of her asserted her purity, her chastity. He groaned.... They lied. In her nature had created a lie....

He tore away his eyes, began to work with feverish energy, ordering Hildegarde here, ordering her there, and she obeyed quietly, intelligently. Potter tested struts and braces, wires and fastenings, controls and motor. He saw to it there were gasolene and lubricant—as far as was in his power he saw to it that his steed of the air should be at its best, potent to give the most that could be demanded of it that night. He looked at his watch.

“Nearly ten,” he said.

“Is it time to start?”

“Yes.”

“What will you do? How will you find him?”

“I’ll sit down on the road he must follow,” Potter said. “I’ll blockade his island. He won’t get past me.”

“In the darkness—”

He pointed through the window. The moon had arisen, silver-cold, gleaming with the rays of a frozen fire.

“Potter—”

“Yes.”

“I’m going with you.... That is why I wore these clothes.”

“Nonsense!” he said, sharply.

“I’ve got to buy myself free,” she said, intensely. “Can’t you understand?... I’ve done wrong.... I was almost a traitor to my country—that I loved. I knew, and I was afraid to tell. I knew her enemies and her traitors—and I knew what they were attempting to do—but I was afraid to tell.... But I did tell, when it was almost too late.... I’m guilty, Potter. It will be with me always, accusing me, if you don’t let me go.... You must see.... There’ll be danger to-night. I must be in danger. I must risk something, everything. I must show that I am willing to die for my country.... Don’t you understand now? I must be willing to offer myself—and I must offer myself.... It’s a ransom.... Then I can come back—if I do come back—and go away and have peace.”

She stopped, drew nearer to him by a step, and let her eyes plead with him.

Like was pleading with like. Her soul called to a soul that was its complement, its counterpart. It could not but understand. Normal considerations failed; nothing about their situation was normal. Potter himself was uplifted, breathing an ether finer, more rarified, more exhilarating than air.... He was not a plodding man of the workaday world that night, but an eager, restless, headlong-questing soul of high adventure.... He understood her; her mood was clear to him. Why should he refuse to her soul what he was demanding for his own?

He bent over her and kissed her, not with the kiss of a lover, but with the kiss of an ascetic. “Come,” he said.

She thanked him silently. “Now?” she asked.

He nodded.

Together they opened the wide doors. In another moment there burst upon them the thunderous roar of the powerful motor, his motor, his country’s motor that was to carry her to victory in her battle to free the world from hideous blackness.

He helped her to her seat, and mounted to his own. In another moment they were moving out upon their quest.