The scene
Water Museum · Canal galleryDuring the opening ceremony, a tiny boat crosses the hydraulic model and disappears into the maintenance tunnel. The audience laughs; the supervisor knows someone altered the demonstration.
Three technicians each had a personal card. Each card allows one fixed action on the junctions. There are no console images, but the system’s operation and the observed route are fully explained.
What we know for certain
Exactly one technician used their own card once between the check and departure. There were no other changes, blockages or failures. Each card carries out the stated action in full, with no additional options. The boat always follows the selected route.
The three accounts
Ada Prat
Lock technician«My card changes the first junction. I cannot choose what the second does.»
Joel Marín
Route programmer«Mine acts on both junctions in a fixed sequence.»
Vera Puig
Model curator«My permission affects only the second junction; I touched nothing else.»
Examine the evidence
0 of 5 openedOpening these five clues does not cost points.
01The complete route
If the first junction is set to A, the boat goes straight to the lighthouse and never reaches the second. If it is set to B, it reaches the second: X leads to the harbour; Y to the tunnel.
02The initial check
Before the intervention, the junctions were set to A and X. A photograph shows both letters unambiguously.
03The three cards
Ada toggles only A to B or B to A. Vera toggles only X to Y or Y to X. Joel toggles the second first, then the first.
04The passage signal
A reliable sensor recorded the boat passing the second junction before entering the tunnel. The tunnel has no other entrance.
05No intermediate changes
The intervention finished before the boat was released. Neither junction changed position while it travelled, and there were no hidden routes.