The investigation is over when the players, through their PCs, cease investigating. What the exact circumstances are when that happens will likely be quite different, but in any case it is up to the players when the mystery is considered solved.
one can obviously partially solve mysteries. I don't quite see what you're getting at.
I mean the mystery has been solved, sure. Your players are probably going to feel like they didn't beat the scenario fully though. I don't see how this presents any issues. I mean there can be a lot of different split outcomes in scenarios like this
No, but they may think they did
Sure. They might find out who did it but fail to discover the person's motives. But those two things are still objective facts that could have been solved
Great! So it seems that all three of you agree that whether or not the mystery is “solved” does not prevent the situation from resolving. Whether the players
succeed fully, succeed partially, or fail altogether at discovering
some, all, or none of the details of the mystery,
play can and does go on. The scenario reaches some form of resolution regardless of how much of the prewritten backstory becomes known to the players. I hope you won't be surprised to know that this is how us narrativists play too when we play with pre-written backstory.
If that’s the case, then when we go back and look at the prewritten backstory, we realize that the only purpose it’s serving is to provide
a scaffolding for play, it’s situational material.
Which leads me back to what I’ve been trying to point at from the start: If the investigation can resolve meaningfully whether the players uncover the backstory or not, then the so-called "objectivity" of the mystery is structurally irrelevant to the experience of continued play. What matters is not whether the GM has a secret answer, but whether the investigation
changes the fiction, the characters, and the stakes — whether the players’ actions materially shape how things turn out.
That’s why I keep pressing on what you mean by “solving” the mystery. Because from everything you've said, it seems like you’re using "solved" as a kind of metaphysical status — something that exists outside and beyond play — when what actually matters is how the investigation procedurally reshapes the situation at the table.
This puts me in a great position to argue that, what I think you all actually mean when you say that there needs to be
a pre-written backstory for things to feel
"real" is something actually a little different. I think what you’re pointing at is the desire you have for your players to arrive at their conclusions by navigating clues and circumstances that present themselves as
objective, external facts via logical extrapolation and a little bit of guesswork
. You want the players’ logical leaps, their deductions, their failures and insights to feel like they are being tested against a solid, pre-existing framework, rather than something improvised in response to their actions.
That’s a valid aesthetic preference. But it’s not the same thing as saying that the existence of that backstory is what makes the mystery “real.”
What makes it real is whether the players' engagement with the investigation carries weight in how the fiction unfolds. You can structure that weight around mental struggle against pre-authored material (the puzzle solving element), sure — but as many on the other side have tried to made clear, you can also structure that weight through emergent, procedural play that makes the ongoing and developing mystery
have real consequences and provoke hard choices on the go.