Hold the Flood — The Exchange

CAM102 · r1 · 2026-09-06 · Campaign and District Designer · In review; proposal. Nothing here is an owner approval, a validated number, or tested behaviour.

District 4 of the seven on Districts. PMR006 assigns CAM102: "deepen the Exchange to the same standard as the three detailed districts." This page does that. The district is the World designer's example (World and Mystery), and the lead's outline at DES104 §3.4 supplies the hall, the drums, the bank, the shut-regime meaning of a dark position, the bank's coupling and the Carrier's part in it. Everything in that outline is kept; this page adds the ground, the panel, the interaction that takes time, two loadouts, a written expedition, the failure case and the asset list. World owns the clue logic; Lead owns any contradiction with the campaign page or the contract.

Sources read 2026-09-06 22:30 UTC. Power and Attraction r4 29f5b0 (the ruled contract: lines conduct when dry; the R1 precedence stack; the Carrier's acquisition range; the Grounder; pursuit range about ten metres; the cable reel; the empty flash; dispatch needs drum and trunk) · Campaign r3 6e4b59 (§3.4, and the panel-table format each district now uses) · PMR006 · Enemies r6 and Combat Rules r5 (the eight-role roster and the composition budget) · Equipment (eight cells, the cable reel) · World and Mystery. Neighbours: Districts · The Collector · The Head-works · Pumping District · Glossary.

1. The problem

Every other district's lever acts on the place you are standing in. This one acts on places you are not, and gives you almost nothing where you stand. There is no salvage here worth the trip, no water to speak of, and nothing to carry home but a setting. A district like that has to earn its expedition some other way, and the answer this page proposes is:

The Exchange is the one district where you must commit to your crowd arrangement before you begin the interaction, because the interaction walks you away from the panel.

The bank's positions are spread along the shaft, in the order the districts sit on the water. Changing which districts the trunk permits means walking the drum floor, and the panel that decides where the hall's crowds are standing is at the other end, by the dock. So the sequence is: read the hall, decide where you want the Flood while you are busy, set the panel, and only then start walking. Get that order wrong and the correction costs the whole walk back.

2. The ground

   DOCK END (south)                                                    HEAD END (north)
   ┌──────────────┐                                                  ┌────────────────┐
   │ EXCHANGE     │   ═══════════ THE DRUM FLOOR (dry) ═══════════   │  THE BANK      │
   │ DOCK         │      one shaft, seven drums, ticking together    │  7 positions,  │
   │ (shelter)    │                                                  │  2 clutches    │
   │  PANEL ──────┼── b1 ────────────── b2 ─────────────────── b3 ───┤  engaged,      │
   └──────────────┘   (dock end)      (mid-floor)      (head end)    │  1 seized      │
          │                                                          └────────────────┘
          │        ~~~ THE TAIL RACE ~~~ narrow channel along the west wall ~~~
          │         (enters by culvert at the dock end, leaves at the head end;
          │          the only water in the district, and what turns the shaft)
          │
    CABLE GALLERY (east wall, head height): every district's signal cable enters here.
                   Lines conduct when dry — this is the district's conduction network.
    ARRIVALS: the upper landing at the head end (the tram pass) — no water route in.

• The drum floor is dry, long and open: one shaft down its length with one drum per district, all ticking together, turned by the tail race at the west wall. The drums are the district's clue and its clock in one object.
• The bank stands at the head end: seven positions, one per district, spread along the shaft in the order the districts sit on the water, and two clutches engaged of a possible three, the third visibly seized. A position's clutch is engaged or not; a district whose position is dark is in the shut regime, never a district with no Flood in it (DES104 §3.4, and PMR004).
• Three fixed beacons, b1 at the dock end, b2 mid-floor, b3 at the head end by the bank. The contract permits more than two (World's fixed contract), and three in one long room is this district's physical signature: the precedence stack is visible here in a way it is nowhere else, because a crowd can see two lit beacons at once and the player can watch it take the nearer.
• The tail race is a narrow channel along the west wall — the only water in the district. It is where the coil works, where the cable reel finds its two wet points, and where an Anchor will be standing.
• The cable gallery runs the east wall at head height. Lines conduct when dry (contract r4 §1), so this is a live conduction network with no water in it at all, and it is what a Grounder climbs.
• Shelters: the dock only. There is no platform on the floor and none at the bank. That is deliberate: the bank is the thing you walk to, and a shelter beside it would delete the district's only pressure.

The panel

Format as DES104 §3 tables each district's.

Note what the intake column does not do. The Exchange has one way in for the Flood — the upper landing at the head end — so the panel here never chooses where a surge enters, only where it goes once it has. This is the only district in the campaign whose panel is purely a lure and not an intake selector, and it is a deliberate contrast: the district that lets you route the whole city cannot route its own front door. Pursuit range here is about ten metres (contract r4 §3), and the floor is wide enough that a body at the gallery wall does not chase a surveyor at the race.

3. Shared-rule diff

Nothing here needs a contract change. That is worth stating plainly: this district is built entirely out of rules that already exist, and the only new thing in it is a machine.

4. Two loadouts that do different things

Eight cells (D023). C coil (2), R cable reel (2), B battery, I insulation, K kit, L portable beacon, S salvage bundle.

The cacher                    The dry hand
B B L C C                     I K S S
I K S                         S S S S
link B1 → C, B2 → L           no battery, no link

• The cacher carries charge into the one district where carrying charge is hunted. The Carrier walks to the nearest reachable loose charge in preference to a lit beacon (contract r4 §3, R5), so a surveyor with two batteries is a moving lure. The cacher's play is to make that deliberate: plant the lit beacon and its battery at the dock end, then walk the floor, so every Carrier in the hall is going the other way. It costs two cells and a battery to buy an uninterrupted walk, and the coil is there because the tail race is the one place a crowd can be stunned.
• The dry hand carries no charge at all and therefore cannot be hunted for it — the Carrier has nothing here to want, and reverts to line 3, the nearest lit beacon. It has four bundles' worth of space for whatever the hall does hold, and it has no coil, no beacon and no way to power anything: it can set clutches, work the panel, and cut. It is the cheapest correct answer to this district and it is also the one with no recovery — if the panel decision was wrong, the dry hand walks back and does it again.

Neither is better. The cacher buys safety in advance and pays four cells for it; the dry hand pays nothing and has no second chance.

5. Discovery

Local question: why do these drums have no water of their own? Every relay the player has met turns on its own race. Seven drums here turn on one shaft, and the shaft comes in from a culvert whose head is out of sight.

• Notice. The drums tick together, exactly, and the shaft enters from upstream.
• Compare. In the pumping district the drum was the clock. Here there are seven drums and one shaft, so the drums are not clocks — they are repeaters.
• Infer. One time source, upstream, permitting all of them. This is the campaign question's first hard evidence, and it is what makes the bank legible: the player understands the lever by understanding the machine, not by reading a label on it.
• Experiment, free, first visit, no item. Disengage one clutch and watch that district's drum stop while the others keep ticking. Nothing is spent and the change is reversible in the same trip.
• Consequence. The bank, §6.
• Recovery if missed. The drums are the floor. Every route from the dock to the bank walks their length.

Campaign clue (the lead's, adopted). The pumping district's dead drum is listed on the bank — a position for a district whose drum no longer turns, still on the board, still with a clutch. Redundant form: the World page's pairing, the pumping district's stopped drum that still hears the trunk's cadence after R is opened. A player who shut that relay meets the same fact from both ends.

What travels. A fact — the districts' relays are repeaters on one upstream clock — and a convention: the bank's board is the campaign's index of districts, so a position with a name the player has not visited is how they learn a district exists. That is how the Collector and others can be found from here without a note being collected.

6. Outward consequence: the bank

The bank's pricing is not restated here. It is stated once, as a rule, in Districts §6 and in DES104 §3.4, and duplicating it is how a wiki grows two versions of a rule. What belongs here is the local half — what setting it actually costs you inside this district:

• Two of seven, and the third clutch is seized. The player is always choosing what to be blind to. The seized clutch is visible from the first visit, so the constraint is legible before it bites, and whether it can ever be freed is the head-works' business, not this district's.
• A swap is disengage, walk, engage. The positions sit in the districts' own order along the shaft, so swapping two adjacent districts is a short walk and swapping the pumping district for the head-works is the length of the floor. The map's shape becomes the cost of the plan, which is the neatest thing this district does.
• The walk is the exposure. There is no shelter on the floor. Whatever the panel was set to when the player left the dock end is what the crowds are doing while they work.
• Nothing is spent. No salvage, no charge, no module. The bank costs a trip and a walk, and that is the whole price — which is why the trip has to be worth planning rather than worth farming.

7. A written expedition — illustrative, not a playtest

Declared setup. Middle campaign. The player wants the Collector permitted (they are going there next, and they want its dispatches announced so a mass can be held deliberately) and is willing to darken the Tram Incline for it. Currently permitted: Tram and Pumping. Rack: the cacher. Panel found on Head — b3 lit, by the bank. Three dispatches at roughly 3, 8 and 12 minutes; the intake is the upper landing whatever the panel says.

• 0:00. The dock. The board reads first dispatch in three minutes. b3 is lit at the far end, which means the first surge will walk the whole floor away from the player — good for the walk, bad for the bank, because the bank is where they are going.
• 0:30. The player throws the panel to Dock, lighting b1 beside themselves, and plants the portable beacon and its battery at the dock end too, twenty metres off. Two lures at the dock end, one of them loose charge.
• 3:00. The dispatch. b1 flashes; the surge enters at the upper landing and walks the length of the floor toward b1, past the bank the player has not left for yet. The player waits at the dock end, at the edge of pursuit range, and cuts the leading edge for the first motes.
• 4:30. The crowd is gathered at b1 and the two Carriers in it are on the planted battery, not on the player's rack. The floor is now empty in the direction the player wants to walk. They start north.
• 6:00. The bank. Disengage Tram — its drum stops, and the board's lamp for it goes out. Walk four positions to Collector, engage — its drum was already turning, and what changes is the clutch. Two engaged again: Pumping and Collector.
• 8:00. Second dispatch while the player is still at the head end. b1 is still lit and still nearer to the landing than anything else, so the new surge also walks south. The player is behind it the whole way.
• 9:30. A Grounder that came in with the second surge climbs the gallery's dock run and grounds it. b1 goes dark. Under R1 the crowd re-evaluates: b2 and b3 are unlit, so there is no other reachable lit beacon, and it spreads along the floor — toward both ends, including the player's. The planted beacon is on its own battery and is not on the grounded run, so it stays lit and holds the Carriers, which is the difference between an inconvenience and a disaster.
• 10:00. The player cannot reach the panel: it is at the dock end, behind the spreading crowd. They discharge the coil into the tail race where the spread has reached the water, stun what is in it, and walk the west wall past the gap.
• 12:00. Third dispatch. The player is near the dock, retrieves the beacon and its battery, and takes the landing route out at the evacuation window with two bundles and a set bank.

What the expedition was about. Not the bank — that was thirty seconds of it. It was about the decision at 0:30, made before anything happened, to spend two cells and a battery on putting the crowd at the end of the hall the player was leaving. A player who walks north with the panel still on Head arrives at the bank with the surge, and the same trip is a fight. The Grounder is what makes the plan expire rather than simply succeed, and the ratified rule — spread only when no other lit beacon is reachable — is exactly what made the planted beacon worth its cells.

Not a playtest. No timing, difficulty or enjoyment claim is made or could be.

8. Entry, revisit, and one consequence of failure

Entry is physical, two ways. The tram incline's summit pass opens onto the upper landing (DES104 §2: the tram's summit is the way to the Exchange). Independently, the trunk signal cable leaving the pumping district's relay room runs here and can be followed on the map. Neither requires a note to be collected; the plans and tags are the ordinary way to learn where they go, per Districts §3.2.

Revisit. Every change to the bank costs a trip here — that is the lever's first price, and it is why this district is visited more often than any other except the pumping district, and always briefly.

One consequence of failure, and it is this district's own shape. A swap is two actions with a walk between them. If the expedition ends in rescue between them, the city is left with one district permitted instead of two. That is not a punishment bolted onto dying; it is exactly what the player did, left half-done.

• Readable before launch. The refuge's board shows which positions are engaged, so the player launches knowing they are down to one.
• What it costs. One fewer district announced until they come back — thinner information everywhere, not more danger anywhere.
• Recovery. A trip here, and the engage half of the swap they did not finish.
• Nothing banked, noted or built is lost. The baseline holds.

And the mitigation is a real choice, not a safety net: a player who engages first and disengages second is never left with one — but they cannot, because only two clutches exist and the third is seized. The seized clutch is what makes the failure case possible, and that is why it is visible from the first visit.

9. Enemy and build pressure

Roles are Combat's, in CMB101 r6 and Combat Rules r5; Campaign owns placement. Everything below works with the Walker alone.

• This is the Carrier's district, and the lead's outline says so. It is the one place the player's own stored charge is a liability with a designed answer — cache it deliberately — rather than a hazard to be endured. Placement proposal for Combat: Carriers present in every surge here, at low density, so the cacher's plant is worth its cells on the first visit rather than the third.
• The Grounder is what makes a plan expire, and this district is where that reads best: the gallery is at head height along one wall, so a Grounder is visible climbing it, and the player watches their arrangement come apart with time to answer. Placement proposal: at most one per surge, and never in the first — the first visit should teach the hall, not the exception.
• Anchors belong in the tail race and nowhere else here: one standing hazard in the only water, so the coil's own working ground is contested.
• What this district does not want: Crusts and Sparks. Both are about water and conduction, this hall has almost none, and putting them here would blur the contrast with the Collector. A district should decline roles as deliberately as it asks for them, and this is the one place in the campaign I would decline two.

10. Asset reuse and gaps

Reused, no new category: drums, cable, poles and galleries, indicator lamps, beacons, a four-position panel, boards, walkway and dock props, a narrow water channel with wet/dry tinting, the humanoid mass.

Genuine gaps, marked and not filled. No free asset has been located, checked or licensed for any of these, and nothing here authorises creating one (Brief D009).

• A long rotating shaft with drums along it — visible rotation, and one drum that has stopped while the others turn. The stopped drum is a clue, so its state has to read at a distance.
• A many-position bank whose per-position state (engaged, disengaged, seized) reads at a glance and in a non-colour channel.
• A long interior hall. This is the only district that is mostly indoors, and it shares almost nothing with the outdoor sets except props.

A cheaper alternative, recorded now. If the long hall is out of reach, the district can be staged as a short gallery with the drums in one view and the bank at its end. It keeps the panel-then-walk decision only if the walk stays long enough to matter — and if the walk goes, this district's only local problem goes with it, which would be the moment to ask whether the Exchange should be a room inside the Head-works rather than a place. I do not think it should, because the bank's price is the trip; but that is the honest fallback and it should be on the record before it is expensive.

11. Open questions and dependencies

• World (WLD103). The campaign clue in §5 is the lead's and the World designer's; the "board as the campaign's index of districts" convention in §5 is mine and is a proposal in World's domain, because it decides how a player learns a district exists.
• Lead (DES104). Whether the panel table in §2 — a district whose panel selects no intake — is acceptable under the contract. I believe it is: the contract requires the intake column to be true, not to have more than one value, and one-way-in is a topology fact, not a rule change. If Lead disagrees, the fix is a second landing and the district loses a good contrast.
• CMB101. The three placements and the two declines in §9.
• EQP101. The cable reel is listed in the contract as joining two wet points; this hall has one narrow race and a dry gallery, so the reel has little to do here and I have kept it out of both loadouts. If Equipment intends the reel to be a general dry-ground conductor, this district would want it — that is a question for them, not a request.
• Unresolved by me, honestly. Whether a district with no salvage worth carrying and one setting to change can hold an expedition's worth of interest on its third visit. My answer is the walk and the panel decision in §7, and I believe it; but this is the district in the campaign whose premise is thinnest, and if any of the seven fails the lead's written-expedition test on contact, I would expect it to be this one. That is why §10 records what it would become instead.