I’ve often found it useful to think of mystery-based scenarios as having two “prongs”: First, the clues required to figure out what happened or is happening. Second, the clues that take the PCs to another location or event where more clues can be gathered.
This is somewhat similar, of course, to the concept of the Second Track, but where a second track presents a secondary set of nodes, here I’m talking about using a single node structure containing two sets of clues.
In practice, of course, you’ll often end up with quite a bit of overlap between the two sets of clues: When the players discover that Altair Electronics is somehow involved with the recent string of cyber-jackings, that tells the players something about what’s going on, but it will also point them in the direction of Altair’s corporate headquarters.
On the other hand, of course, there’s also the exception which proves the Three Clue Rule: In certain mystery structures you can actually be certain that the PCs will know about some locations without needing three clues. (Or any clues.) For example, if they’re police officers tracking bank robbers and another bank gets robbed, they’re going to get called to that location.
In such scenarios, of course, you can simply focus on delivering the clues necessary to reveal the mystery. (With three clues per necessary revelation.) But when faced with a more traditional two-prong approach, the important thing to understand is that you can spread the clues necessary to solve the mystery thinly (as long as you include the necessary density of clues to keep PCs moving from node to node). There may be entire nodes where there are no clues for unraveling the deeper mystery – just clues for moving on to the next node (where, hopefully, answers can be found).
How thin can you go? Well, it depends on what effect you’re trying to achieve. If you’ve got a mystery that’s serving as the metaplot of an entire campaign, for example, you may be spreading those clues very thin indeed.
Another option, of course, is to vary the clue density. Nodes that are difficult to find or difficult to exploit (due to armed resistance, for example) might offer more rewards in terms of mystery-solving clues.
Or perhaps the deeper you move into a conspiracy, the more clues you might discover. For example, the early stages of a layer cake node design might have only sparse or enigmatic clues. The deeper you move into the scenario, however, the thicker and more explicit the clues might become.
Conversely, it’s important to remember not to mistake mystery-solving clues for node-transition clues. What I mean is that including a mystery-solving clue in a node doesn’t actually satisfy the Inverted Three Clue Rule: If it isn’t helping you find another node, then it doesn’t count towards the “necessary” quota of clues for keeping the adventure in motion.