In this acclaimed philosophical comedy of manners, a hotshot lawyer (Matthew McConaughey), his career rocketing upwards, loses concentration momentarily and becomes the perpetrator of a hit and run. An insurance claims manager (Alan Arkin) with a troubled family life has a pleasant but irritatingly jovial colleague. A finicky physics lecturer (John Turturro) is having a meticulously timetabled affair as a stock response to a mid-life crisis, something his wife (Amy Irving) discovers after his recently stolen wallet is returned to her by a conscientious citizen. Meanwhile, cleaner Beatrice (Clea DuVall) is forced to reconsider her idealistic approach to life after being hit by a life-changing accident and an unwarranted accusation. Most of these people cross each other's paths in some way, sometimes casually, sometimes prodoundly, their conversations in all cases leading them to a greater understanding of the "one thing" of the film's title: the elusive nature of happiness.