A through line is a connecting theme or plot used in media such as films and books. it is sometimes also called the ‘spine’, and was first suggested by Konstantin Stanislavski as a simplified way for actors to think about characterization. He believed actors should not only understand what their character was doing, or trying to do, (their objective) in any given unit, but should also strive to understand the through line that linked these objectives together and thus pushed the character forward through the narrative.