Read in Judith Merril’s The Year’s Greatest Science Fiction and Fantasy, 1956.
Nice little story featuring the awfully nice Mr. Johnson, who spends his day in New York being rather helpful to people who cross his path. After a busy day doing good, he returns home to his wife, who has spent her day out and about, but doing quite the opposite. It appears that they alternate their roles.
No explanations, and minimal sfnal elements.