Then the latch slipped back with a jar that sounded horribly loud, and she waited, trembling and trying to keep calm.

Since Mabel had not heard the noise, it was plain that she was asleep and somebody else was in the house.

Still Mabel, if awakened, would not be of much help, and remembering that the pistol was in her room, Agatha went down the passage.
The passage was very cold, a curtain swayed in an icy draught, and she found the door of her room open.

Stopping for a moment, she thought there was somebody inside.

This, however, might be a trick of her imagination, and although she wanted to steal away, she knew that if she did so she would lose her self-respect and the confidence she would need for her journey to the North.