After making rapid progress through the plot detail of Acts I and II of my narrative, I am finding things slowing down as I reach the synopsis for the Acts III and IV, where the narrative builds to its climax and the eventual denouement in Act V. Although it is frustrating to experience this slowing in speed, I have decided that it is actually good thing. After all, this is where the various strands in the plot come together, conflict increases and is resolved. So if I breezed through it, that might mean that actually my plot was very simple and obvious, which isn’t what one would really want from a mystery.
I think it is also indicative of using the snowflake method, in that you start with the broad concepts and then have to fill in the details. At this stage of the synopsis I find that I am having to back track a fair bit and change things. But, again this is a good thing, as it is easier to do this at synopsis stage rather than while writing the first draft.