It is of small consequence that they could not find it in their power to be in tune with the virtuous Rodneys: the Rodneys were conditions, not effects.
However that may be, it was Katherine Rodney, pretty, plump, and spoiled, who pulled the first stone from the foundation of Medcroft's house of cards.

Katherine had convinced herself that she was deeply enamoured of the volatile Freddie; the more she thought that she loved him, the greater became the conviction that he did not care as much for her as he professed.

She began to detect a decided falling off in his ardour; it was no use trying to hide the fact from herself that Constance was the most disturbing symptom in evidence.

Jealousy succeeded speculation.

Katherine decided to be hateful; she could not have helped it if she had tried.
It was very evident, to her at least, that Freddie was not to blame; he was being led on by the artful Miss Fowler.