The key was in the lock.

It opened outwards, and there she found herself, to her surprise, in the heart of another dwelling, of lowlier aspect.

She never saw Robert; for while he approached with shoeless feet, she had been glancing through the open door of the gable-room, and when he knelt, the light which she held in her hand had, I presume, hidden him from her.
He, on his part, had not observed that the moveless door stood open at last.
I have already said that the house adjoining had been built by Robert's father.

The lady's room was that which he had occupied with his wife, and in it Robert had been born.

The door, with its trap-stair, was a natural invention for uniting the levels of the two houses, and a desirable one in not a few of the forms which the weather assumed in that region.