Crawl of Cthulhu – The Brockford House

Photo by Andy Davey.

Spoilers for “The Brockford House” scenario below!

Available in the Call of Cthulhu Rulebook (2nd through 4th Editions), “The Brockford House” is very similar to the AD&D module U1: The Sinister Secret of Saltmarsh. The adventure starts with the exploration of the Brockford House, our Cthulhu Crawl’s equivalent of a castle keep. This eventually leads to the sub-basement where a stone altar must be tipped over in order to descend into the caverns below. The previous owner worshiped Cthulhu, and Deep Ones serve as the primary Mythos antagonists, and, unless replaced, added thematic elements and clues should hint at their presence. 

Below we examine the locations in “The Brockford House” and provide some suggestions to add depth to the adventure using the elements described in our introduction to Call of Cthulhu dungeon crawls. We provide maps for reference, but having the scenario on hand provides valuable context. Feel free to modify or draw inspiration from this discussion as you prepare to send your investigators into this eerie cliffside home. 

Ground Floor: 

Move the deer head to the parlor!
  • Original: 5 rooms, but only one of actual interest (study), the remaining four rooms contain no clues or interactions.
  • Revised:
    • Study: Split the collection of hidden books and their spells, but provide a Clue in the Notes from Necronomicon to suggest one (R’lyeh Text) is stored elsewhere (see Sub-Basement). 
    • Parlor/Dining Room: Move the unusual deer head to this room, add fireplace Passage controlled by deer head (leading to the upper floor, see below)
    • Kitchen: Add Interaction (caretaker NPC) to this room behaving suspiciously around the open fireplace. With the successful use of social skills, he offers his keys for investigators to borrow (see Guest Room below).
    • Guest Room: Unusually large room with connection to the basement. Add Trap with blood-stained and scratched floorboards hidden beneath the bed (0/1D3 Sanity Loss) as a result of nocturnal visits from Deep Ones. The door to the basement is locked (Obstacle) and requires the caretaker’s key, Locksmith skill, or physical force to open. 
    • Bath: add some suspicious elements, including unusual fishhead bath fixtures and tentacular claws on the enormous bathtub.  

Upper Floor:

  • Original: no discoveries to further investigation, repeated creepy element from study and evidence of human captive
  • Revised:
    • Bedroom 1: Add Clue by placing dusty boxes of records, including house building plans and a schematic of a basement excavation noting a “sinkhole” in the location of the trapdoor. 
    • Games Room: Add Treasure (key to unlock basement trap door) discovered by Spot Hidden contained in a disturbing chess set with Mythos-inspired pieces. Second malformed deer head with fireplace passage, as above. 
    • Master Bedroom: Contains a Clue in Brockford’s diary that the bank is unable to locate the original deed for the property (later found in Caverns, Area C)
    • Barren Room: Curiously barren and smaller than expected, Idea or Spot Hidden roll to identify a false wall, which hides a crude cell with iron staples driven into stone used to hold chains, a name is scratched into the stained floorboards. 


  • Original: hidden marked trapped door, requires digging in the correct location (with no assisting clue) or successful Listen roll.
    • Lots of consequences for breaking the lid, but no provided reason why the investigators delay searching the sub-basement immediately 
  • Revised: 
    • Provide Clue as discussed in Upper Floor, Bedroom
    • Opening the Trapdoor Lid: Use the key found in Games Room or rely on brute force STR, tools, or firearm to remove the lock. 

Sub-basement: a small room with carved stone walls and a hollow altar stained with old blood.

  • Original: contains a hollow altar (for no defined reason), and a defaced wall with no clue
  • Revised: 
    • A successful Spot Hidden identifies a seam in the altar, which allows investigators to open a panel containing the remaining Mythos tome (R’lyeh Text, English translation), opening the container releases another Trap, as it also contains a broken, crumbling Cthulhu idol (1/1D2 Sanity Loss)
    • If investigators recover the idol, the previously unintelligible defaced markings disturbingly clarify into a stylized depiction of Cthulhu.

Caverns: the true meat of this dungeon crawl. As written, exploring the caverns risks much danger with limited reward. We add some suggestions to incentivize exploration and set up a dramatic escape.  Present a delay in exploration by using high tide to fill the caverns with water, which allows the deep ones an opportunity to strike at night.

Layer One:

Crude Interpretation of Layer One
    • Area A: Spot Hidden to note footprints clustered around a crude altar hidden among stalagmites. Add an opportunity to Track, which indicates the presence of deep one sentry and reveals a clear path to hidden Area C. 
    • Area B: Deep One sentry is a Wandering Monster, and we change the chances of encountering him on D6 to:
      • 1-2: Hiding in hole leading to Layer Two (Hard Listen to detect)
      • 3-4: Stalking area by the water (Spot Hidden to detect).
      • 5-6: Not present, but failed group Stealth check alerts deep ones to the presence of investigators
    • Area C: Entirely up to Keeper discretion, but we opt to move the corpse of the Brockford House’s former owner to a visible position dangling from the cavern ceiling by a chain as part of a terrible sacrificial ritual. The deed is visible sticking out of the raincoat’s top pocket, and the investigators must complete a Skill Challenge to successfully lower him (Locksmith, Mechanical Repair, etc.). In the process of completing the skill challenge, they discover Passage to Layer Two. 
  • Layer Two: 
Cruder Interpretation of Layer Two
    • Area D: more interesting if only Passage from Area A leads to this location. Consider this the primary location to encounter a group of Deep Ones forcing investigators to flee back to the house, attempt to swim out, or push deeper into the network of caves.  As suggested in the adventure, swimming out through the water leads to the open ocean providing an Escape.
    • Area E: as written this room contains only bones, including those of humans. Add Treasure in the form of a single deep one speargun
    • Area F-K: as written, nothing except 10% random encounter. In addition to Wandering Monsters, populate the caves with Treasure (gold coins), Interactions (captive tourists), and Clues, which point to the location of the underwater deep colony or further elucidate the nefarious schemes of the house’s former owner, which involve the summoning of a terrible being using the Transport Cube (Area M). All these discoveries provide the incentive to explore, create meaningful choices, and add complications. 
    • Area L: excellent alternative location for Passage from Area C. Offers danger in form of mud slick, but allows investigators to avoid immediate detection and permits free exploration of nearby caves. Allow the underwater passage to lead both to the deep one city and surface (Escape). 
    • Area M: As written, this contains Treasure in the form of the Transport Cube. Consider adding a Boss Fight when the removal of the cube results in the appearance of a Dimension Shambler, Star Spawn, Hound of Tindalos, or other Mythos monster of your choosing. 

 By adding to the layers of mystery at the Brockford House, investigators find plenty of motivation to continue crawling through this dangerous dungeon. The scenario affords a very open-ended conclusion depending on what the investigators uncover beneath the house, and how they wish to address the Deep One infestation. Jon Hook also has a nice discussion about using the Brockford House as an adventure scaffold in Modern Mythos, Episode 9. In his rendition, he moves the Brockford House from coastal Maine to the shore of Lake Superior (a great call!).

1 thought on “Crawl of Cthulhu – The Brockford House

  1. Matt McCloud says:

    This is super cool! The only difficulty I see is that unlike the Saltmarsh scenario, once my Call of Cthulhu players see the entrance to the caverns, it would be a big “nope” from them to go further without some SERIOUS incentive, like rescuing a kidnapped person about to be sacrificed or something.

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