throughline
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.
Produced by none other than Seth Rogen and Evan Goldberg, Good Boys again most closely resembles a kind of junior-varsity tryout for that duo's Superbad, down to its modestly affecting emotional through-line: an acceptance of the fact that childhood friendships, forged out of proximity and convenience, aren't always destined to last.
A railway route that passengers can take without needing to change trains.
Where it comes from
From through (“passing from one side of something to the other”, adjective) + line. Compare Middle English thurghline (“a brail or buntline”).
Adapted from the Wiktionary entry throughline (CC BY-SA 4.0).