The Great Prince Shan by E. Phillips Oppenheim

It chanced that the box was empty when Maggie, with flying footsteps, hastened down the corridor and pushed open the door. She sank into a chair, her knees trembling, her senses still dazed. Deliberately, although with hot and trembling fingers, she folded over and tore into small pieces a programme of the dances, which she had picked up from an adjoining chair. The action, insignificant though it was, seemed to bring her back into touch with the real and actual world, the world of music and wild gayety, of swiftly moving feet, of laughter and languorous voices. For a brief space of time she had escaped, she had wandered a little way into an unknown country, a country from whose thrilling dangers she had emerged with a curious feeling that life would never be altogether the same again. She glanced at the clock at the back of the box. She had been absent from the Hall altogether only about an hour and twenty minutes.

There was still at least an hour before it would be possible for her to plead weariness and escape. And opposite, in the shadows of the distant box, the mock Prince Shan seemed always to be gazing at her with that cryptic smile upon his lips.