Falling Man concerns a survivor of the 9-11 attacks and the effect his experiences on that day have on his life thereafter. As the novel opens, Keith Neudecker, a 39-year-old lawyer who works in the World Trade Center, escapes from the building injured slightly and walks to the apartment he previously shared with his son Justin and estranged wife Lianne. After a period of convalescence recuperating from the physical and mental trauma experienced in the attack, Keith resumes his domestic routine with Lianne while at the same time broaching a romantic relationship with a woman named Florence, another survivor, whose briefcase Keith absently took with him from a stairwell upon exiting the tower. Lianne meanwhile grows frustrated with a neighbor in her building who loudly plays middle-eastern sounding music, witnesses the dissolution of a writing group she ran for Alzheimer’s patients, and spends time with her elderly intellectual mother Nina and her boyfriend Martin (an art dealer who may or may not have been involved with a Baader-Meinhof-like terrorist group in Germany in the 1960s). In the second half of the novel, Keith eventually abdicates his partially-resumed domestic life and begins touring the world playing in professional poker tournaments full-time, recalling his weekly poker nights with co-workers, one of whose deaths he witnessed on 9-11.
Throughout the book, Lianne sees a performance artist dubbed "Falling Man" in various parts of the city. Wearing business attire, he suspends himself upside-down with rope and a harness in the pose of the man in the famous photograph of the same name by Richard Drew.