His very kindness in letting her return was his offence.

Elfride had her sex's love of sheer force in a man, however ill-directed; and at that critical juncture in London Stephen's only chance of retaining the ascendancy over her that his face and not his parts had acquired for him, would have been by doing what, for one thing, he was too youthful to undertake--that was, dragging her by the wrist to the rails of some altar, and peremptorily marrying her.

Decisive action is seen by appreciative minds to be frequently objectless, and sometimes fatal; but decision, however suicidal, has more charm for a woman than the most unequivocal Fabian success.
However, some of the unpleasant accessories of that occasion were now out of sight again, and Stephen had resumed not a few of his fancy colours..