There was no use in angering Drummond further.

Instead, she let him think that he had succeeded in frightening her off.
She went back to her own apartment to wait and worry.

Evidently Drummond was pretty sure of something, or he would not have disclosed his hand to her, even partially.

She felt that she must see Kitty before it was too late.

Then the thought crossed her mind that perhaps already it was too late.