She shrank away from him in nameless terror, gasping and panic-stricken.  “Nick,” she whispered, “are you—­mad?”

He answered her jerkily in a strangled voice that was like the snarl of a beast.  “Yes—­I am mad.  If you try to run away from me now—­I won’t answer for myself.”

She gazed at him with widening eyes.  “But, but—­” she faltered—­“I—­I don’t understand.  Oh, Nick, you frighten me!”

It was the cry of a child, lost, bewildered, piteous.  Had she withstood him, had she sought to escape, the demon in him would have burst the last restraining bond, and have shattered in one moment of unshackled violence all the chivalrous patience which during the last few weeks he had spent his whole strength to achieve.

But that cry of desolation pierced straight through his madness, cutting deeper than reproach or protest, wounding him to the heart.

With a sound that was half-sob, half-groan, he turned his back upon her and covered his face.

For a space of seconds he stood so, not moving, seeming not even to breathe.  And Muriel, steadying herself by the mantelpiece, watched him with a panting heart.

Then abruptly, moving with a quick, light tread that made no sound, he crossed the room to one of the wide-flung windows and stopped there.

From across the quiet garden there came the strains of “The Blue Danube,” fitful, alluring, plaintive—­that waltz to which countless lovers have danced and wooed and whispered through the years.  Muriel longed intensely to shut it out, to stop her ears, to make some noise to drown it.  Her nerves were all on edge, and she felt as if its persistent sweetness would drive her mad.

Surely Nick felt the same; but if he did, he made no sign.  He stood without movement with his face to the night, gripping the woodwork of the window with both hands, every bone of them standing out in sharp, skeleton lines.

She watched him, fascinated, for a long time, but he did not stir from his tense position.  He seemed to have utterly forgotten her presence in the room behind him.  And still that maddening waltz kept on and on and on till she felt sick and dazed with listening to it.  It seemed as if for the rest of her life she would never again be free from those haunting strains.

The soft shutting of the window made her start and quiver.  Nick had moved at last, and her heart began to throb thick and fast as he turned.  She tried to read his face, but she could not even see it.  There was a swimming mist before her eyes, and her limbs felt powerless, heavy as lead.

In every nerve, she felt him drawing near, and in an agony of helplessness she awaited him, all the surging horror of that night when he had drugged her rushing back upon her with tenfold force.  Again she saw him as she had seen him then, monstrous, silent, terrible, a man of superhuman strength, whose mastery appalled her.  Again in desperate fear she shrank from him, seeking wildly, fruitlessly, for a way of escape.