Julian Treslove, a professionally unspectacular former BBC radio producer, and Sam Finkler, a popular Jewish philosopher, writer and television personality, are old school friends. Despite very different lives, they've never quite lost touch with each other - or with their former teacher, Libor Sevcik. Both Libor and Finkler are recently widowed, and together with Treslove they share a sweetly painful evening revisiting a time before they had loved and lost.

It is that very evening, when Treslove hesitates a moment as he walks home, that he is attacked - and his whole sense of who and what he is slowly and ineluctably changes.