Did you write to the middle of Act 3? What do you MEAN you didn't get there yet? You're an author, not a turtle--GET IN GEAR.
You've moved into Act 4? But the writing guides talk about three acts, not four?
I say, GO 4 IT. If your story needs a fourth act--if that last twist brings a whole new set of complications--TWIST MORE. Keep the tension high, maintain a rocket pace, and follow this tale anywhere. We love the surprise of plots that turn, but the twist has to seem plausible. Your readers should think, Wow, I should have realized he would do that.
Your plot will feel spontaneous if it evolves from your characters--and yes, you do have to stream to the end so you don't frustrate or bore the readers--but somewhere along the way, you'll need to make a pit stop.
The "Next Move" Pit Stop
If character interactions are driving your plot, stop halfway through the last act--whether that's 3 or 4-- and review the means, motives and opportunities of your suspects, in a new way. Review timeclocks and pacing. (Can this event happen at midnight if it was 7pm two minutes ago?) Head into your final resolution with your ducks in a row, but without knowing the end.
How can you keep yourself and your readers guessing? I want you to make a fricking chart. Each PLAYER in this novel--every character who has the power to determine the end--each one of them has a next step in mind. So on your chart you write:
Name -- What He Wants - His Main Obstacle - His Angle - His Next Move
What's his angle? If you know your characters, then you KNOW how this one thinks. Is he angry right now? Star-struck in love? Does he want to protect someone at all costs? Sure, that's part of motivation, but I'm talking 'bout RIGHT NOW. At this moment, what does it all come down to for this character?
Now look at the "room" of characters on your paper? Who's the strongest? Who's the smartest? What event might change that mix? If character A does his Next Move, how does that affect everyone's dynamics.
This isn't a chess game. Don't plan out the end with a series of next moves, just do this one set of moves--
And let your ending EXPLODE.
