Between Seasons 1 and 2 of Voyager, there is a dramatic change in the character of Seska:
In particular, she
becomes a villain.
Seska appears in a number of Season 1 episodes prior to the 12th episode, "State of Flux", where we find out that she is not as she seems.
Was this development in Seska's character part of the planning of the series itself? Or did the writers only conceive of it when writing "State of Flux?"