So, I deduce, the original idea was one third of a story idea.
Happens all the time. Partial ideas, that is. One third is actually a fairly large chunk; I've had ideas that generated a much smaller chunk of the final story before I had to tease out the rest.
And I have some ideas what is going to happen next. How to defeat an already introduced supervillian (but that's going to have to be the future, since she has yet to meet the ally), how to meet the Love Interest (which is also going to have to be the future, but more quickly, since it just needs to get her somewhere else).
It's the join to those ideas that is interesting.
The fun part is that I know, looking back, that I may be utterly unable to tell which parts were the original inspiration, and which the stuff dredged up to cement them together.