Kate Gunzinger is a mathematics professor at a Chicago university. She lives with a man, named Homer, in a comfortable but not terribly passionate relationship.
Kate travels to New York for a job interview and to attend the wedding of her widowed father. She meets the bride’s son, Ben Lewin, a former professional baseball player.
Ben is married, but a relationship develops with Kate. He takes her to Yankee Stadium for an old-timers’ day ceremony, and eventually, they have an affair. When they part, Kate goes back to Chicago and breaks up with Homer, not knowing what the future holds.
The first scene shows Kate Gunzinger in a lecture giving a correct proof of the snake lemma from homological algebra