Serials conformed to a rather strict formula
The beginning would be the unravelling of the "cliffhanger" that ended the previous episode. In the very first serials, silents, it would be an actual scene hanging over a cliff, often of the heroine, sometimes called Pearl Pureheart, but also of the hero.
The remainder of the episode would be the buildup to the new crisis. Each crisis, when unravelled, was not the same as the one built up to. How could it be? It was inescapable!
it is extremely interesting to watch a whole serial back to back to back. Seeing the subtle changes made in both editing, and content--the movie magic that permits escape. Some of these serials had two editors; they needed them.
Much of the modern language of action movie editing grew out of serials.