Mrs. Ames by E.F. Benson

Three days later Major Ames was walking back home in the middle of the afternoon, returning from the house in which he had lately spent so considerable a portion of his time. But this was the last day on which he would go there, nor would he, except for this one time more, cross the threshold of his own house. The climax had come, and within an hour or two he and Millie were going to leave Riseborough together.

Now that their decision had been made, it seemed to him that it had been inevitable from the first. Ever since the summer, when, from some mixture of genuine liking and false gallantry, he had allowed himself to drift into relations with her, the force that drew and held him had steadily increased in strength, and to-day it had proved itself irresistible. The determining factor no doubt had been his quarrel with his wife; that gave the impulse that had been still lacking, the final push which upset the equilibrium of that which was tottering and ready to fall over.