The scene
Toy Museum · Night-time modelA small locomotive disappears from a model through a maintenance hatch. To open it, two numbered tokens are inserted into a lantern; its display retains their sum until the next reset.
Three staff members received sealed pairs for the demonstration. The lantern showed nine when the empty space was discovered. The returned envelopes reveal which pair could have produced that reading.
What we know for certain
One of the three people opened the hatch and removed the locomotive using their two assigned tokens. The display adds the printed numbers, with no other operations. Nobody mixed pairs, added tokens or reset the lantern. There was only one opening during that interval.
The three accounts
Lidia Roca
Museum guide«My pair was the one listed on the first envelope.»
Mateo Serra
Model mechanic«I kept my tokens together. I did not open the hatch.»
Nora Acuña
Coordinator«I did not exchange any pieces with the others.»
Examine the evidence
0 of 5 openedOpening these five clues does not cost points.
01The retained reading
The lantern showed 9 after the removal. Its log confirms that this number came from the two tokens used in the only opening.
02Lidia's envelope
Lidia received one token marked 2 and another marked 4. The envelope's labels are original.
03Mateo's envelope
Mateo's pair consisted of one token marked 3 and another marked 6.
04Nora's envelope
Nora received two separate tokens, each printed with the number 5.
05The verified operation
The mechanism adds the two values exactly once. It does not concatenate digits or use the order in which the tokens enter.