Can you chart a murder? How to build an interactive novel

[Editor’s Note: I asked Antony to detail the process by which he created his interactive crime novel, Can You Solve The Murder?, which required some specific tools and a lot of intricate planning. And of course this article contains no spoilers for the book or any of Antony’s work.—J.S.]

I’m an author, primarily writing crime and thriller novels. I’m best known for the Cold War spy movie Atomic Blonde, which was based on my graphic novel. I also write the Dog Sitter Detective murder mysteries, the Brigitte Sharp spy thrillers, and most recently the interactive novel Can You Solve the Murder?

Hang on — an interactive novel? That’s right. You see, in addition to all the above, I also write video games. I grew up loving both books and games of all kinds, and was fortunate (read: old) enough to have been a young boy when the original Choose Your Own Adventure, Fighting Fantasy, and Lone Wolf books were first published.

Branching Out

Those series are examples of what came to be called ‘gamebooks’, because they’re both forms smushed into one; books where the reader plays an active part, directing the story by making choices, like playing a game. (These days we sometimes get fancy and call them ‘interactive novels’.) This is achieved by dividing the story into numbered sections and sending you to read different sections depending on your choices.

If you’ve ever played a text adventure game on a computer…

The ‘Lords of Time’ text adventure. (Wikimedia)

…Then you’ve essentially played a gamebook, just with all the page-flipping done for you by the computer. The modern ‘Visual novel’ form is basically the same thing, too.

We call these types of story a branching narrative, because the choice map often looks like a tree, with each new section branching off into further choices.

Simplistic example of a branching narrative.

At their heart, all video games are essentially branching interactive experiences. You make a choice — whether in text, or with a joystick, or by pressing an action button — and something happens in the game reflecting that choice. The presentation of those choices, and the results, is nowadays enormously more sophisticated and complex than it was in a 1980s text adventure. But at their core, all games are about players making choices and the system reacting to them.

Back in the late ’70s & ’80s, computer games looked very much like that screenshot above. They weren’t the interactive movies with ultra-realistic graphics, hours of cinematic music, and dialogue voiced by professional actors to which we’ve become accustomed. Instead, they were basic, often poorly-written, and any graphics were extremely primitive. Those early limitations allowed gamebooks to thrive. They were almost always better-written than computer games, with richer and more evocative text, and were also often illustrated by professional artists.

As video game technology accelerated, though, and digital interactive experiences became ever more realistic and immersive, gamebooks fell out of fashion. They became a curio, remembered with nostalgia by enthusiasts but largely forgotten by the mainstream.

I was one of those enthusiasts from the very start. In fact, I was so taken with gamebooks that eleven-year-old me even had a go at creating one of my own, written on a manual typewriter and illustrated with a ballpoint pen, which I then made my friends play. Sadly, the ambitiously-titled Hellfire of Death’s Caverns is lost to the mists of time, but looking back, it certainly explains a lot about my career.

You see, a love of gamebooks introduced me to early role-playing games and fantasy board games, which in turn led to an interest in game design… which ultimately led to me working in videogames as a writer and narrative designer. That career has run in parallel with my fiction writing for the past twenty years1, and more recently I’ve also established myself as an award-winning crime author.

Charting a Course

I love writing and plotting crime and mystery fiction. I love writing and designing games. So I kept wondering: was there some way to combine the two?

That’s when I remembered the many hours I spent as a boy with my head buried in gamebooks. Was it possible to write a crime story in that format? How would I handle clues, red herrings, and all the other elements that people love about murder mysteries?

And how on earth do you plan a book like that, anyway?

While answers to many of those questions would take months of work to figure out, the last — how do you plan a gamebook? — was one to which I already knew the answer thanks to that early typewritten effort, and my later experience in game design: you build a huge flowchart.

The original gamebook authors drew their charts and maps by hand, on taped-together pieces of paper, with markers. If you’ve ever mapped a text adventure game in a notebook as you played, you were effectively doing the same thing in reverse.

Nowadays, though, we have better tools. Digital tools. Surely one of them would be better suited to making such a flowchart. But which one?

There are quite a few apps and services out there with which to build flowcharts. I was already familiar with Miro, an online service used by many game designers for brainstorming and building ‘paper prototypes’ (while there’s no paper involved these days, the name has stuck). I used Miro to plan a couple of proof-of-concept interactive short stories, which I wrote to get a handle on the format and test whether I could make it work.

A flowchart for a branching narrative short story. That tangle in the bottom left shows why fine-tuned control over directional arrows is essential.

I could, and friends to whom I sent the prototypes enjoyed them, so I began planning a book-length mystery.

But Miro is a subscription service, with only a small number of ‘boards’ available to free accounts. I was already at my limit, and reluctant to subscribe — believe me when I tell you that very few authors actually make a living writing novels! So I put aside the decision of what to use for a moment and focused on pitching the book itself. After all, if it didn’t sell, there’d be no need to build charts.

I needn’t have worried. Can You Solve the Murder? 2 went to a bidding war, and was eventually acquired by Transworld in a two-book deal with a frighteningly short deadline. The matter of choosing a flowcharting tool had now become rather urgent.

My criteria were simple, but specific. I wanted to:

Lay out the chart in a freeform manner, rather than being forced into a grid, with no limit on size or dimensions

But have the option to snap-align objects to one another

Draw arrows that snap to destination objects with auto-applied directional heads, and that can be moved and modified freely later

Easily apply text labels to arrows that represent a choice (most do, but not all) and have those labels move with the arrows when modified

Draw multiple such arrows coming from a single object

Have multiple arrows also arriving at a single object

Mix object shapes, and be able to easily resize and re-color them however I wish

Write text directly into any object, and have the text be easy to modify: size, color, style, etc

Overlay shapes on top of one another (in order to track section numbers and clues discovered)

Finally, I needed it to feel intuitive and simple to use. While that’s not really a quantifiable metric, it was important to me. I knew I’d be spending many, many hours making and using these charts. As a former graphic designer, not to mention lifelong Mac user, I want my tools to get out of the way and let me work, not make me wrestle them into submission.

I spent the next couple of weeks trialling many different charting apps and web services. I won’t go into detail on them, but suffice to say that while several had the features I was looking for, none of them felt particularly easy or intuitive to use…

Return to #1 and Try Again

…Except Miro, to which I kept returning. So I sucked it up and used part of my book advance to pay for a subscription.

Ultimately, the best tool had to win out. I’m a big believer that using inferior tools simply isn’t worth the hassle and frustration they cause, no matter how cheap they may be, and while Miro still isn’t perfect (it doesn’t do per-character text sizing, and object color modification could be better), it remains the tool best suited to how I build gamebook flowcharts. In some ways, using Miro reminds me of a good vector design app, like the venerable Aldus FreeHand3 or modern Affinity Designer, with an ease to its interface and UI that at times becomes almost invisible (the highest compliment I can pay an interface).

So, how do I use all those features I mentioned to build a gamebook flowchart? Well, let’s take a look.

Only five colors, sorry.

Colors: Green boxes represent ‘core story’ sections, which all readers will see, while yellow boxes are sections that will only be seen by readers who make particular choices. Blue boxes are ‘ghost’ sections — they don’t exist in the book, but here they note where a choice will send you to a different part of the chart. Dark green boxes are good endings, while black boxes are — you guessed it — bad endings that require you to return to #1 and try again.

Pet the dog, be rewarded. If only real life were so simple.

Overlaid objects: Each main colored box has a numbered red circle overlaid on it at top-right — this is the number of that section in the book, to which you flip when directed. Some boxes also have a blue circle bottom-right for Clue Numbers, which I’ll explain below.

Text inside any object: In addition to text in the main boxes, the number codes in those red and blue circles are contained directly within the object, rather than being a separate text box placed on top and grouped. This sounds like a small thing, but it makes them much easier to manipulate, edit, and move around the board, and when you’re dealing with literally hundreds of these objects, it makes a big difference.

Grid alignment: Although most of the boxes are aligned with one another by choice, note that section #52 is not. This tangle demonstrates the value of not being forced into a grid:

Freeform arrows: Many boxes have multiple arrows branching out of them, and #46 even has multiple arrows branching into it. That’s an essential requirement. Again, that tangle reinforces the need for fine control over arrows.

Arrow labels: These show which section a choice (or conditional: see below) directs you to read next.

The blue circles are part of a system I call Clue Numbers. Many sections of Can You Solve the Murder? ask the reader to write down a Clue Number. In this example, the text of section #23 would end with the instruction:

Write down D2 in your notebook, then turn to #46

Later, if you decide to keep walking and thus turn to section #9, a conditional check is made. The text of that scene would end as follows:

If you have D2 written in your notebook, turn to #32

Otherwise, turn to #58

This mechanic is vital to the success of a clue-based mystery like Can You Solve the Murder? because it effectively allows the book to ‘remember’ your choices, and the information you’ve gathered, throughout the story — but does so in a way that doesn’t give the game away, because the reader doesn’t know what those codes mean. (I do, of course, and track them all in a spreadsheet).

It’s impossible to complete Can You Solve the Murder? without using Clue Numbers. Thus, it’s vital that I can easily assign them to the appropriate sections and move them around if need be when building the book’s flowchart.

Sharing the Load

One nice element of using an online service is shareability. This was necessary for Can You Solve the Murder? because of something called ‘structural edits’. In fiction writing, this is what happens after you submit your first draft, and the editor then suggests changes such as removing/adding subplots, modifying characters, perhaps re-ordering some scenes, and so on. All these things change the structure of the book, hence the term.

Making such large-scale changes to a gamebook manuscript would be absolute hell.

Every choice in a branching narrative sets off a cascade of subsequent choices and reactions, meaning structural changes ripple downstream throughout the book. In a regular novel, revising a manuscript to remove a secondary character can often be accomplished fairly easily. In a gamebook, though, it might require re-plotting half the story, creating new sections, re-ordering existing paths… a nightmare that could take weeks or even months to untangle.

To avoid this, I gave my editors password-protected view-only access to the flowchart board, something Miro makes very easy (I could also have given them full editing access, or not required a password), and asked them to make their structural edit notes based on the flowchart. None of us had ever worked on a book like this before, and doing so required a lot of mutual trust, especially with strange requests like this! But it worked out, and part of that was down to how easy Miro makes sharing and viewing.

You can also easily export a Miro board, or part of one, to a variety of formats, including JPG, PDF, and even CSV. While I haven’t needed that facility for Can You Solve the Murder?, I use it often in my video game work.

The truth is that I barely use a fraction of Miro’s power. There are Miro wizards out there who can make it do all sorts of things: presentations, prototypes, slideshows, you name it. I’ve worked with some of them at game studios. Apparently, even the NFL’s digital team uses it to plan gameday strategy for their apps and services. Miro’s YouTube channel has many such case studies, along with tutorials.

Me? I don’t need to do any of those things, and wouldn’t know where to start. But that leads me to the final thing I like about Miro: it doesn’t force that stuff on me.

One of my favorite and most-used apps is the writing software Scrivener, which I’ve used since it first launched in 2007. (I’m writing this very article in it.) A common refrain amongst its advocates is that most people only use 20% of Scrivener’s features… but we all use a different 20%. Miro feels very much the same.4

Choose Your Own Learning

I expect most of you reading this aren’t writing interactive novels. But you might need to create charts or diagrams of some kind, and if so, I recommend Miro. Yes, there are free alternatives out there, but I haven’t found any that are as flexible and intuitive to use.

As for the book, Can You Solve the Murder? was published in summer 2025 and quickly became my best-selling novel ever. A sequel, The Forest of Death, is due this year… and yes, I used Miro again to build its flowchart.

My first game was the original Dead Space, on which I started work in 2006. Since then, I’ve written titles like Resident Evil Village, Dead Space Extraction, Shadow of Mordor, CSR Racing (which was featured in an Apple keynote!), Binary Domain, and many more. ↩

As part of promoting the book, I also designed an interactive live event in which the audience must solve a (different) murder. You can hear me host one such scenario on an episode of The Incomparable’s Game Show podcast. ↩

To this day, I still mourn the passing of FreeHand. ↩

One friend who saw an image of my flowcharts asked if I was using Twine, which is an interactive fiction tool that allows you to write branching narrative charts and then export the result as a playable game. People have made amazing, complex games in Twine, and I sometimes use it myself for proof-of-concept work (such as testing a game’s romance system, or checking dialogue tree logic). But Twine’s interface is often frustrating and slow, and it wouldn’t allow me to do even half of the things I set out in my criteria list. ↩