You've got factual consistency licked.
Some astute reader points out that the cook couldn't possibly have had time to walk into the village and back in between Uncle Herbert's bathtime and the discovery of the missing cruet set in the middle of the croquet lawn.
And if Aunt Maud really could see the summerhouse from her lawn chair, then she couldn't possibly have also observed the twins duelling by the Fountain of Eternal Mediocrity because of the twelve-foot-high privet hedge in the way.
Because, while you were busy with factual consistency, you got ambushed by it's twisted sidekick...logical consistency!
Outcome - logical consistency
This is all about making sure your facts also abide by the laws of physics, geometry, chronology, human psychology, or whatever laws are relevant to your world and important to the story.
This alone is a huge topic, so I won't try to hit it all at once. This post will concentrate on causality, dependency, and chronology - making sure things happen in a logical order and in a plausible time.
In many stories, this is not a huge problem. Sequences of events happen one after another, and it's pretty clear which needs to go before which. But if you have a complicated plot, where many threads are going on at once, and especially where who knows what is important, then things can get messy real quick.
A picture is worth a thousand words
Think of an Agatha Christie mystery. My head hurt tracking all the movements of people around the boat in "Death on the Nile", and to be honest, even if there was a logical inconsistency there I'd never have spotted it.
I don't know how Agatha Christie plotted those stories, but most people need some kind of tools to help manage webs of intrigue like that, and mostly this involves some kind of visual depiction of relationships.
One of the simplest is a dependency network. This kind of diagram has two simple features: things that happen are shown in boxes or bubbles; important relationships are shown as arrows connecting things that happen.
Things that happen can be things people do (like Uncle Herbert takes a bath, or the cook walks to the village), or events (like Aunt Maud sees the twins duelling). For simplicity, I'll refer to all of these as "actions", even though some are passive (like seeing something happen).
Relationships show some kind of dependency between one action and another. These may be:
- Directly causal - Action A causes Action B to happen. For example, Jeeves entering the Flamingo Drawing Room at an inopportune moment causes Delilah to flee in panic onto the verandah.
- Dependent - Action A logically must happen before Action B. For example, the cook has to discover the antique silver cruet set is missing before the search for it can begin. You could argue that this is also causal - the discovery caused the search - but that is only partly true. There were choices to be made first (announce the loss, or conceal it, or pack bags and set sail for Brazil...). The key thing is that the search couldn't logically begin before the discovery.
- Or required by the story - it is important for Action A to happen before Action B. For example, it is important that the cook leave for the village before Jeeves enters the Drawing Room, otherwise she'd see a semi-naked Delilah running onto the verandah, which we don't want her to know about.
The diagram as a whole must have a direction of flow, usually either top to bottom, or left to right. Use whichever direction works best for you, but choose one and stick to it. Arrows can go with the flow, or be slanted at an angle across the flow, but they cannot go against the flow.
This is what ensures causal consistency and avoids chains of events that try to turn on themselves and eat their own tails. If you can't arrange things so that the arrows all go with the flow, then you have a logical inconsistency somewhere.
Here is a network diagram from the start of Electrons' Breath, where I was trying to sort out the interactions between the main players as various threads of events unfold.
Please accept my apologies for the handwriting! This shows just how quick and dirty these tools can be. Great for roughing out first thoughts.
The beauty of network diagrams is that they are simple and scalable. You might use one to map out a whole novel, or simply to make sure that a messy fight scene hangs together. You might limit it to just the major plot, or delve into all the twists and turns of sub-plots. Wherever you have a mess of things going on, this might help you to keep things straight.
Time, gentlemen, please!
So, maybe you've got the cook toddling off to the village at the right point in the story, but returning again only minutes later because her departure and return are logically sandwiched between two other events. But the village is a fifteen minute walk away, and the cook isn't all that young or sprightly, and she's bound to stop for a pick-me-up at the Jolly Ploughman...oops! Your network diagram didn't show up that little problem because all it cares is that things happen in the right sequence.
Where time is important, you can turn to a related tool called a Gannt chart. This is essentially a network diagram with a measured time scale along the direction of flow. Instead of simple boxes or bubbles for actions, the length of the box now shows duration and its position on the page shows when it happened. Everything above still holds true, except now you have to make sure that you have room for the right sized boxes.
This can show up temporal inconsistencies, like where you haven't left enough time for a series of events to happen. It can also show up the less obvious opposite problem, where your character on one thread is going to end up twiddling his thumbs for an embarrassing length of time while waiting for something else to happen.
While network diagrams are easy to sketch out on a piece of paper, Gannt charts take a lot more effort to draw. If you are going to do things like this, you might consider drawing software that lets you move whole blocks of activities around together, or even project management tools like MS Project. However, I think you'd have to have a pretty complex plot before you needed industrial leverage like that.
Let me check my calendar
The chances are, if you have concerns about temporal consistency, you can probably get away with a related but much simpler tool: a calendar, or timeline. This focuses just on the timing of events, rather than all the causal relationships between them.
Without all the arrows to worry about, you can knock up timelines quite easily in tables, maybe using Excel. Here, your activities are in cells, and each row (or column, if you are going left to right) represents a unit of time. This makes it very easy to lay out a series of actions one after another, and make sure they will fit into the time available. If you need to move blocks around, you just have to make sure they still occupy the same number of time units. This is easy in a spreadsheet using cut/paste.
I used this approach to map out the main outline of Ghosts of Innocence. Here, time flows down the page, and each row is a day.
This kind of approach still lets you check for some causal consistency, providing you don't have too many dependencies. You can lay out several different threads in parallel on the same timeline, and make sure the important points where they cross paths coincide. In this example, I use arrows >> and << to show where events need to stay lined up.
In the swim
This chart also illustrates another useful technique.
Just as the position and size of a box on the page can show you time and duration, you can make use of the other dimension to show some other key information. In this example, while the rows show time, the columns show the main groups of characters. This is then called a swimlane diagram, because your activities are confined to swimlanes running either down or across the page.
Keeping everything related to a character together in a swimlane helps keep track of who's doing what, as well as when.
Back to the theme of logical consistency, this helps to ensure that you don't end up with people trying to do things in two places at once.