The Bones Beneath London: Creating a TTRPG Module

How do you create a murder mystery TTRPG module?

Notes are spread across the table. The investigators lean closer, their voices overlapping as they revisit the evidence. Someone points out a detail that was overlooked before. The mystery does not solve itself, this is where the story truly comes to life.

Hi there! I am Iris and over the past five months I have worked on creating my own murder mystery TTRPG module. This project was a part of my internship with VALUE Foundation and has been a whirlwind of research, writing, doubt, excitement, and maybe too many documents named “final_v3_really final.”

In the last blog post, I explored immersion and how the GM and players can shape the mystery together. This time, I will explain the final part of the process: playtesting the game, revising it based on feedback, and turning all of this into a document that makes sense to someone who does not live in my brain.

Testing the Waters

A playtest is exactly what the name suggests: testing the game by playing it. The goal is not just to see if the story works, but to understand how other people experience it. Are the mechanics clear? Does the investigation flow? And most importantly: is it fun? To deal with these somewhat scary questions, I turned to the wonderful world of the internet to read some guidelines on how to prepare a playtest.

Ideally, I would have tested the module with one GM and five players to cover all character archetypes. In reality (as usual), ideal conditions did not exist. Instead, I was lucky enough to work with four wonderfully creative players and a GM who is an absolute mastermind when it comes to storytelling. I prepared several documents, such as character creation guidelines, system explanations, and the clue trail for the GM. These texts later became the backbone of the module chapters. As the session lasted only 1 to 1.5 hours, the group played roughly a third of the story. The ending remains a mystery, which honestly felt very on-theme.

Watching the playtest was surreal. Seeing people interpret clues, argue over theories, and fully engage with the world made the story feel alive in a way it never had on paper. My strange and vague ideas had turned into something shared, which was easily the highlight of the entire process.

Revisiting the Case

Of course, playtesting is not just about vibes: it is about the participants’ feedback. I prepared for receiving input by reading about how others approach playtesting. I noted my own points for observation, sent out a good ol’ Google Forms, and spent time discussing first impressions with the group after the session. This helped me identify what worked and what did not. Players especially enjoyed the details that made the story feel historically grounded, and appreciated the freedom to interpret clues creatively. The GM’s additions and interpretations were fascinating, as it showed that I should indeed leave room for improvisation.

However, one element proved to be a problem: the system itself. Whilst the players agreed that GUMSHOE works for investigative scenarios, they felt that constantly naming specific abilities made interactions feel stiff and unnatural. The system did its job, but it felt like an visible tool rather than an invisible framework. For this module, the system should feel intuitive and with the limited time I had left, I knew I could not overhaul the system entirely. Instead, I prioritised adjusting the presentation: rephrasing rules, encouraging implicit ability use, and reducing how often players needed to explicitly call out mechanics. It’s not a perfect fix, but it’s a meaningful step forward.

Making the Module

After processing all feedback, I returned to the drawing board. I outlined the full module, decided on the order of chapters, and wrote introductory sections to guide readers through the story. There is no secret trick here: I just had to sit down and… do it. Somewhere along the way, the working title stuck and became the actual title: “The Bones Beneath London.”

So… where is the module? The document will be published very soon on a dedicated project page (with an actual PDF, so exciting!). Keep an eye on this website if you are curious.

There are still things I want to expand on: deeper historical appendices, more beginner-friendly guidance, as well as illustrations and page design. In the wise words of Ariel the mermaid: I want more. That said, I’m incredibly proud of what I created in the time I had. And to answer the question I asked in my very first blog post: yes, it is absolutely possible to create a TTRPG module from scratch! If you’re thinking about undertaking a similar project: please try. Thank you for joining me on this journey!