Then all was quiet and dark again.

She had slid quickly out and the door had swung to behind her.

Another instant and I heard the click of the key as it turned in the lock, heard it and made no outcry, such the spell, such the bewilderment of my faculties! But once the act was accomplished and egress made difficult, nay, for the moment, impossible, I felt all lesser emotions give way to an anxiety which demanded immediate action, for the girl had gone out without wraps or covering for her head, and my experience of the evening had told me how cold it was.

I must follow and find her and rescue her if possible from the snow.

The distance was long to town, the cold would seize and perhaps prostrate her, after which, the wind and snow would do the rest.
Throwing myself against the door, I shook it violently.