Sandy Petersen’s “The Haunting” is said to be the single most widely played Call of Cthulhu scenario of all time.

The reason for its popularity could not be more clear: It literally teaches you how to play the game.

“The Haunting” is not just a classic adventure; it is by far and away the most widely-played Call of Cthulhu adventure and remains the most frequent point of entry for players who are new to the system. The reason for this enduring popularity is that it teaches you how to play and, more importantly, how to run an investigation-based RPG.

Back in the early 1980s, most people who played RPGs played dungeon-crawls. Dungeon crawls are a fairly straight-forward and self-explanatory form of adventure as they involve a series of self-contained rooms that serve to place an upper limit on how much players and DMs are expected to have on their plates at once.

Some rooms contain puzzles, some rooms contain roleplaying opportunities, and some rooms contain monsters to kill. These various elements can be more-or-less involved depending upon the level of the group, the imagination of the players, and the ambition of the DM but at the end of the day dungeons present you with a series of self-contained problems that can be worked through until every room is clear.

One of the ways in which dungeons can be complicated is by having the players uncover something in one room only for it to serve as a solution to a problem in another room. This may sound like no complication at all but, for most beginning players, the idea of keeping track of stuff you have picked up and thinking it might be useful at a later date is not obvious.

The problem with investigation-based RPGs is that the adventures are generally nothing but series of elements that need to be written down, remembered, and brought into play at some later point in the adventure. Maybe it’s an object to be used in a ritual. Maybe it’s a piece of information found in a library. Maybe it’s something an NPC happened to say when you were asking them about something completely different. For reasons that probably deserve a longer post, gamers tend to struggle with the process of collecting, processing, and acting on clues. This isn’t to say that gamers are stupid (though they are… ugly and smelly too), it’s just that solving mysteries tends to involve a set of skills that take longer to learn than the skills required in clearing out dungeons.

What this means is that a lot of people will hear about Call of Cthulhu, want to give it a try, and then be completely baffled as to how to actually play the bloody thing. This was true in the early 1980s when Sandy Petersen first wrote the adventure and it is true now when many people’s first experience of table-top gaming is the hyper-tactical playstyle baked into Dungeons & Dragons.

“The Haunting” works because its story has a classic three act structure:

The group begins by doing research into the house and the family that fled. Aside from teaching players that the first step in an investigation-based RPG is always to hit the books and grab as much publicly-available information as possible, it also primes the emotional pumps by giving you a bit of generalised lore. There’s the family forced to flee, the frequent changes of ownership, and the ties to a sinister cult. This stuff functions a lot like the Harbinger in a horror film, the old guy who has seen some shit and begs you not to visit the old abandoned dildo factory before relenting and telling you that there was definitely some shit to be seen. This priming of the emotional pumps is really important as it not only gives the players the permission to act scared, it also tells them that something freaky is going to happen and so they will naturally respond to every ambiguous thing with a degree of trepidation.

Then the group make their way into the house and Petersen presents the GM with an amusingly linear map:

The house is literally just a series of corridors with numbered rooms!

We’re back in the dungeon but rather than presenting the players with a series of self-contained challenges, Petersen gives us a series of creepy abandoned rooms across which are scattered some clues that need to be pieced together before the level boss can be defeated. The clues are not all that demanding, the goal here is to teach the GM how to set the mood and generate a particular atmosphere. With the emotional pumps having been primed in the opening section, it should be fairly easy to get the players jumping at their own shadows but Petersen also gives the GM tools with which to stir the pot in the form of sinister magical effects deployed by the monster in his lair. “The Haunting” is sometimes known by the title “The Haunted House” but a more apt description would be to call this section of the adventure a ghost train or a fright maze as this section of the adventure works like a fairground attraction: The players are strapped into a little cart and wheeled through a series of rooms while the GM sits in the control booth hitting the ‘dry ice’ and ‘maniacal laughter’ effects before having skeletons and spiders drop onto the party.

Though fairly simplistic and incredibly under-stated in the text, this section is an absolute masterclass in horror gaming. In the forty-odd years since the publication of this scenario, horror gaming has made a few innovations but the bones of the genre are found in this here adventure: Prime the pumps with lore, dress the rooms with creepy imagery, have shit jump out at players until they start unloading their shotguns at every looming shadow and creeping door.

The adventure’s conclusion is another example of how Petersen sets out to teach people how to run Call of Cthulhu as the final confrontation takes place in a small room and Corbitt’s powers are described in detail as are the tactical moves he is likely to make. Petersen talks about how Corbitt will protect himself from bullets, how elements of the setting can be used to harm him, and how to deploy his mind-altering spells.

Without even knowing it, people who play this adventure will have been given a solid grounding not only in how to play an investigation-based game, but also how to run one. Chaosium were quick to acknowledge the canonical nature of “The Haunting” by inviting Keith Herber to write an expanded version for inclusion in The Trail of Tsathoggha.

I don’t think that this expanded version of “The Haunting” has ever been re-printed and in fairness, all Herber wound up doing was transplanting the action to a bigger house, replacing the level boss with a slightly shitter character, and burying the location of the final room under dozens of tedious diary entries.

Far more effective were adventures such as Michael DeWolfe’s “Mr. Corbitt” and Mark Morrison’s “The Crack’d and Crook’d Manse”, which took the basic structure of “The Haunting” and altered it in interesting ways. For example, DeWolfe stresses the mundane nature of the adventure setting before pumping the gas and sending the entire adventure hurtling off the rails into the splatterpunk grotesque while Morrison increases the number of clues scattered about the house and makes the final confrontation more frightening and less mechanical in its resolution. All three adventures are brilliant and different in their own ways but all of them share that three act structure laid down by Sandy Petersen.

In fact, 40 years after its first publication, “The Haunting” remains so fresh and so potent that contemporary writers can basically just release a re-skinned version of the exact same adventure and still wound up having that adventure be well received.

Also brilliant (and sadly overlooked) is the way that Petersen scatters the adventure with plot hooks for future sessions. He even sets up a cult that could serve as an antagonist for an entire campaign. Most people tend to overlook Petersen’s willingness to do things like this but these types of adventure hooks are really important in whetting the players’ appetites and making them want more. If a session of “The Haunting” ends with the group announcing that they want to track down the Chapel of Contemplation then you are already about half-way to running your first campaign.