Action vs Surprise
Nowadays I would probably be able to predict what was going to happen in most episodes but back then, when audience expectations were different and I was a child, their schemes were genius.
Excitement in books is often equated to action - a fight, a chase, a death defying leap - and it is true that action can help to maintain pace. As a reader, as well as a writer, I enjoy the thrill of a heart wrenching escape as much as anyone. However, there is one other element that can occasionally work just as well.
Surprise your reader. Throw something into the mix that they could never have dreamt up in their wildest dreams. Get their heart thumping, not through a chase or a fight, but through a shock. Wow! I really didn't see that one coming. She can't be his sister, surely? He was wearing a mask? He's a quadruple-agent on the run from smuggler nuns?
Sometimes the unexpected can be just as exciting as action.