So your players have just crashed in on your nefarious mastermind behind the current adventure. After some light banter, one of your players make an unexpected maneuver and may possibly end the encounter prematurely. You really hadn’t planned for them to punk your billy bad guy, but they are a creative lot. What should you do?
Well, if you are like me you may have a tendency to to use your on-the-fly thwarting spell. This is like a contingency spell, but it magically conforms itself to thwart any actions of a player character that may end a scene prematurely. I can not say how much this irritates players, and rightly so. If your players feel that whatever they do has no effect on the game, they may loose interest. Your players want to be epic, and they want to do it their way.
So what do you do? Let them have their moment. If a player jumps up and fires an arrow at their nemesis during the recital of his dastardly plan and manages to score a critical hit, maxing out damage, and some how causes enough to just barely knock him unconscious… let him. It might not be the way you planned it to go down, but your players will talk about it for years to come. Remember, you control the rest of the world and they may have punked that necromancer, but what did they do about all his minions? That abused young man the character rescued could, in fact, be be a fiercely loyal apprentice to the necromancer.