Every day Iona Iverson, a stylish, opinionated, larger-than-life magazine advice columnist, rides the train to work with her dog, Lulu. Every day she sees the same people, whom she knows only by nickname: Impossibly-Pretty-Bookworm and Mr-Too-Good-to-Be-True. Of course, they never speak. Seasoned commuters never do.

Then one morning, the man she calls Smart-But-Sexist-Manspreader chokes on a grape right in front of her. He’d have died were it not for the timely intervention of Sanjay, a nurse, who gives him the Heimlich maneuver.

This single event starts a chain reaction, and an eclectic group of people discovers that talking to strangers can teach you quite a bit about the world around you—and even more about yourself.