I always had mixed feelings about a recurring villain in this kind of series. They are usually the same as the regular perps you see in all episodes, except that they have the ability to keep escaping - which is the case of Nicole.
The upside is that sometimes you can have a villain that has been built up enough for the viewer to ask: is he/she capable of doing all this? Can she be the puppet-master of all this mystery? How can one person really pull this off? That is the question you keep asking the entire episode: it has to be Nicole (again - sigh), but how? This time the viewer is finally surprised, even if you figure it out slightly before the very end.
The upside is that sometimes you can have a villain that has been built up enough for the viewer to ask: is he/she capable of doing all this? Can she be the puppet-master of all this mystery? How can one person really pull this off? That is the question you keep asking the entire episode: it has to be Nicole (again - sigh), but how? This time the viewer is finally surprised, even if you figure it out slightly before the very end.