The sound came again-so unmistakably, this time, the sound of a footstep in the soft, squashy ooze on the Heath, there could be no question regarding the nature of it. Miss Lorne came to an instant standstill and clutched her belongings closer to her with a shake and a quiver; and a swift prickle of goose-flesh ran round her shoulders and up and down the backs of her hands. There was good, brave blood in her, it is true; but good, brave blood isn’t much to fall back upon if you happen to be a girl without escort, carrying a hand-bag containing twenty-odd pounds in money, several bits of valuable jewellery-your whole earthly possessions, in fact-and have lost your way on Hampstead Heath at half-past eight o’clock at night, with a spring fog shutting you in like a wall and shutting out everything else but a “mackerel” collection of clouds that looked like grey smudges on the greasy-silver of a twilit sky.She looked round, but she could see nothing and nobody. The Heath was a white waste that might have been part of the scenery in Lapland for all there was to tell that it lay within reach of the heart and pulse of the sluggish leviathan London. Over it the vapours of night crowded, an almost palpable wall of thick, wet mist, stirred now and again by some atmospheric movement which could scarcely be called a wind, although, at times, it drew long, lacey filaments above the level of the denser mass of fog and melted away with them into the calm, still upper air.