The second act sags before you write it

A second act that sags is usually a planning problem wearing a writing problem's clothes: the screenplay ran out of promise, not out of events.

When a middle drags, the first instinct is to add. A new character, a reversal, a set piece, a betrayal. The middle gets busier and still does not move, because a middle does not run on events. It runs on consequence: each decision costing the person who made it more than the last one did. An event only carries a cost if something was already owed.

So the useful question about a sagging middle is not what happens next. It is what is owed, by whom, and when it comes due. A story that has promised nothing by the end of the first act cannot be rescued in the second, because there is nothing there to spend. The sag is not a hole in the plot. It is a hole in the ledger, and the ledger was settled before the pages began.

That is why the middle belongs to planning. By the time the writer is typing, what each scene owes is already fixed by what the beats before it promised. A beat is a promise; a scene is what the promise costs. What reads as a scene that will not work is usually a beat that never made a promise, and no amount of rewriting the scene can pay a debt nobody took on.

Beatstack plans the middle as sequences with a page target, counted against the pages actually written. The place a story goes quiet is a number on the board before it is a feeling at the desk. That is not a cure. It does tell you whether the problem in front of you is a scene to rewrite or a plan that stopped three sequences ago.

The second act is not where a story is invented. It is where the first act's promise is paid, in public, one scene at a time. When the middle sags, look at what was promised rather than at what was written.