Years ago a common criticism of Call of Cthulhu‘s investigative adventures was “if the players fail a single Spot Hidden roll to find a clue, the adventure is over.”

I think that’s mostly a lazy critique. It’s like saying if your D&D players never find the dungeon, the adventure is over.

But there is some truth behind it. Some RPGs, especially horror ones like Call of Cthulhu or Vaesen, lean heavily on investigative adventures. Unlike a typical fantasy adventure, like a dungeon or an epic quest, investigative adventures are written more like the outlines of a TV episode. These adventures are designed to feel more like the source material they are emulating, like a good horror story or a Sherlock Holmes adventure. They have plots, backstories, characters with relationships, twists, and clues. Lots of clues.

Clues can make or break investigative adventures. Ideally, clues will appear, provoke thought and debate, create more options for players, and then move the game along towards an epic ending. But placing clues is an art. Unlike a troll guarding a door, a clue can easily be missed!

And, one person’s “that was so obvious” clue is another player’s “oh my God how would you expect me to ever find that?!” one. Your players’ abilities to find and put clues together can vary a lot!

I played in a game once where we were trying to solve a murder. We missed the one clue in a garbage can — no one thought to look — and we spent an hour touring various nearby diners, gyms, and libraries and never found a single plot hook. Yes, the GM gave us agency to miss clues and do what we wanted, but no, we didn’t feel like we were making any progress. Bad GMing? Probably. Bad adventure writing? Definitely yes.

But if clues are too obvious, the adventure feels linear. If you examine a crime scene and find threatening note from the neighbor in the victim’s pocket, well, you’re 100% going to visit that neighbor next. There’s little agency there, either.

Gotham City in 1939…

This month’s adventure is Gotham ’39 – The Mirror Eternal, a pulp noir mystery set in the 1930s of Gotham City. The investigators aren’t caped crusaders —they’re skilled but ordinary investigators, fighting against corruption and crime with luck, wit, and determination.

Gotham ’39 features both linear sections and open-ended ones, which I think is a strong way to build an investigative adventure. The adventure starts with a murder, one the PCs witness. The superstitious mob boss Santo Cassamento is gunned down at a nightclub, and something weird is going on with his body. There are a few scattered clues, but more importantly, the PCs soon find themselves blackmailed and told to meet at a secret location later that night… or else.

It took me forever to place clues in this adventure. I used lots of player feedback and even technology (thank you Notebook LM!) to constantly place, replace, and rethink clues. Where was Batman when I needed him?

But in the end, I think it worked, and players will navigate this adventure feeling both smart and like they have real agency. So, here’s my best advice to placing clues in your RPG adventure:

Use Different Types of Clues

Very aware that players have different relationships with clue-finding, I made sure to use lots of different types of clues:

Physical evidence. These clues are the typical ones — paper in desk drawers, shards of glass in a mobster’s pocket, photographs in a safe. Some are hidden and some are obvious. I also like to reinforce physical clues with handouts, which gives your thoughtful players something to look at and feel as they are putting the mystery together.

Witness testimony. There are a lot of NPCs in Gotham ’39, and I doubt most groups will encounter half of them. But I made sure that every NPC possesses a clue… if the PCs can pull it out of them. Of course, finding these clues requires the right combinations of diplomacy, fast-talking, and intimidation. By hiding clues behind NPCs with big personalities, roleplayers and social skill-loving players have ways to move the adventure forward.

Research. Some players love the part of the mystery where they hit the library. I intentionally added a library for those players who like to bias towards research when they get stuck. Generally, my library clues overlapped with other clues, but provided more detail. Sure, you could hear a reporter tell how the Beretti crime family once blew up a building, but the library gave you more details on it.

Contacts. I made sure that the PCs started the game with a few contacts. In GURPS, this is easy because there’s literally a Contacts advantage which lets you reach out and ask for advice. But even with other RPGs, give your PCs a few key contacts at the beginning — an old newspaper editor friend, fellow Jazz musicians, whatever.

Redundant, Redundant Clues

I always make sure that two similar clues are placed at two different locations. In Gotham ’39, for example, the PCs can find a copy of a ritual page which is key to understanding what’s going on. But the ritual page can be found in three different locations, because they were owned by three individuals. This means missing a clue isn’t a big deal… it will likely be found later.

Clues Should Have Consequences

Some clues trigger strong reactions from some key NPCs. This makes finding clues feel less ordinary, and more exciting, or even dangerous. For example, there are two smuggling rings in Gotham. If the PCs disturb either of them (which is highly likely!), the bloodthirsty smuggler kingpin will come after them for vengeance. When the world reacts to clue-finding, it feels more real.

Secret Clues

I placed some difficult-to-find clues that will reward players who comb over every detail, but won’t stop the investigation if not found. For example, in one location there’s a hidden safe. If the PCs find it, they can find photographic evidence that will take down a mobster. This can give them a huge advantage in the investigation, but if they don’t find it, that’s okay, they’ll have to just find a different mobster to influence.

A Tangled Web… and Gencon Incoming!

Despite all of this careful placement, I’m 100% positive I missed things, and that there are potential dead-ends or hiccups in this adventure. I’m planning to run it at Gencon this year, so I have a few more months to iron out the details. If you get a chance to run it ahead of that convention, let me know in the comments below how your group fared!

Get Gotham ’39 – The Mirror Eternal FREE here:

Powerful mob families are tangled up in something dark—something they don’t understand. The whispers say they are summoning a demon, but the truth is stranger. As the players dig deeper, the bodies pile up, the lies get thicker, and a new villain steps from Gotham’s shadows.

• Gotham ’39 (GURPS Pulp Noir)
• Gotham ’39 (GURPS Pulp Noir) – Printer Friendly
• Gotham ’39 (Pulp Call of Cthulhu)
• Gotham ’39 (Pulp Call of Cthulhu) – Printer Friendly
• Gotham ’39 – VTT Assets

Related: More Obvious Superheroes