I spent an awful lot of my youth playing role-playing games.
Like most people I started with the gateway game that was Basic D&D - this was the 1980s - and then moved on to harder stuff like Runequest, Traveller 2300, and, of course, Call of Cthulhu. Those afternoons and evenings spent adventuring with my friends are an enormous influence on what and why I write. Like a lot of authors, I was almost always the GM and much of the time I made up my own scenarios. So when a friend asked me recently to GM a game for a weekend away with some old pals, I jumped at the chance to write my own adventure. I wanted to do a traditional horror tale, set in a remote corner of the Scottish Borders, and had lots of fun coming up with a simple - one might even say, derivative - adventure idea. I also knew I wanted it to be what RPG players call a 'sandbox' adventure.
There are essentially two types of role-playing game scenario: linear and sandbox. A linear scenario is all mapped out, a sequence of events that take place in a particular order and the players simply follow it from beginning to end. It's very reactive, with most of the decisions the players make being around how to handle what’s thrown at them. The GM has a lot of control, and the players have very little freedom to choose their path. This can make for an easy-to-run adventure but for experienced players it can be very limiting. They have no real agency and are just there to be thrown around by the GM's inventiveness.
A sandbox scenario is very different. In this, there is no linear narrative line. Instead, the GM has a bunch of non-player characters with motivations, various settings for stuff to take place, some key clues linked to revelations that will drive the story forward, and possibly a schedule of events that will happen if the player-characters don't intervene. The players are free to do what they want, go where they will. There is no clear path. The GM has to be open to anything and must know all the elements well enough to react, support or thwart the unexpected things that players always come up with.
Putting together a sandbox scenario is like doing all the preparation for writing a story but then leaving it before the heroes turn up. There have to be well-defined supporting characters, a coherent backstory, an engaging setting and so on, but the 'writing' ends when the main characters arrive. The author has only limited control over where the story goes. And that's the point of a sandbox scenario. Everyone writes the rest of the story together, contributing to the narrative, building it as a group. When it works, it's the kind of experience that makes table-top role-playing games such a wonderful social, shared experience. All the people around that table become bound together as active participants.
This lack of control means some kinds of GM hate sandbox scenarios. These little dictators are known as 'frustrated novelist GMs'. They just want to tell their version of the story, using the players to push their narrative line. The players are puppets, pawns for the GM to write the novel they can't be bothered writing the normal way. This kind of GM is constantly frustrated because the players are not making the 'right' decisions or following his or her creation 'properly'. This egotistical approach completely defeats the purpose, makes the game about the GM and not about the collective experience.
When we were playing the horror scenario I'd put together, I thought I'd done it all correctly. No fixed narrative, no linear progression, just a collection of clues and characters plus the occasional prod if the players were wandering too far away from the solution. But as the night wore on, I realised I was doing something wrong, something I could only articulate after reading about sandbox scenario design in the Call of Cthulhu rulebook. I realised that, though I was delighted the players were solving the mystery in their own way, my frustration stemmed from my having a very specific final confrontation in mind. But, as the book said, when it comes to sandbox scenarios, Never Write The Ending.
This is the oddest thing about putting together a sandbox adventure for anyone accustomed to writing fiction. Forget about the ending. If you have too fixed an idea of the conclusion in mind, your will just be constantly battling against the players when they want to go their own way. This was a complete revelation to me, so un-novelistic, such a radically different approach to writing a story. It forcibly reminded me that role-playing is collective story telling. The GM's job is to get the story moving and to keep it moving, to know how the world will react to the player's decisions but the story is what everyone tells together.