rocking horse qustion

Lawrence builds anxiety through Hester's reactions, as she stands just outside Paul's door. It's as if she's afraid to turn the handle, and yet, in most cases a mother's instinct would have had her opening the door without hesitation. Why did she wait.

And then, because of the strange anxiety at her heart, she stole upstairs to her son's room.  Noiselessly she went along the upper corridor.  Was there a faint noise?  What was it?

She stood, with arrested muscles, outside his door, listening.  There was a strange, heavy, and yet not loud noise. Her heart stood still.  It was a soundless noise, yet rushing and powerful.  Something huge, in violent, hushed motion. What was it?  What in God's name was it?  She ought to know.  She felt that she knew the noise.  She knew what it was.

Yet she could not place it.  She couldn't say what it was.  And on and on it went, like a madness.

Softly, frozen with anxiety and fear, she turned the door-handle.