throughline

noun2

1. •
   In full through line of action: a theme that runs through the plot of a book, film, or other narrative work, or a series of such related works.

   • The Russian rockets fell on Babyn Yar, 80 years after the Nazi atrocities it commemorates; Zelenskiy’s face was enough to hammer home the gravity of the thematic throughline. — 2022
2. •
   A railway route that passengers can take without needing to change trains.