The Black Files · September 30, 2026 · Difficulty: Cadet
Black File #103 — SolutionThe Service Corridor
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The case
Elena Patel, concierge, was found dead at The Hollis Hotel at 8:40 PM. Seven people were at the scene. Exactly one of them was alone with Elena in the same zone.
The evidence (9 clues)
- Connie was in the Service Corridor.
- Elena was standing on the stairs.
- David was sitting on the sofa.
- Fabian was in the Bar Lounge.
- Bianca was in the Lobby.
- Gloria was in the Service Corridor.
- Connie was standing on the stairs.
- Angela was the easternmost person at the scene.
- David was the northernmost person at the scene.
The answer
The killer: Bianca Hoffman, alone with Elena Patel in the Lobby.
Fixing rows and columns from the extreme-position clues cascades through the board and leaves Bianca alone with Elena in the Lobby.
Step-by-step deduction
- Before placing anyone, each clue eliminates cells:
- • Angela: was the easternmost person of all, and since there is one person per column somebody occupies column G: that is Angela; row 5 belongs to Connie; row 1 belongs to David; row 6 belongs to Elena; nobody else can occupy row 7, so it must be Angela. Only G7 is left.
- • Bianca: was in the Lobby; row 5 belongs to Connie; row 1 belongs to David; row 6 belongs to Elena. Only B4 is left.
- • Connie: was in the Service Corridor; was on the stairs; column G belongs to Angela. Only F5 is left.
- • David: was sitting on the sofa; was the northernmost person of all, and since there is one person per row somebody occupies row 1: that is David; column F belongs to Connie; column E belongs to Gloria. Only C1 is left.
- • Elena: was on the stairs; Elena cannot be in the Bar Lounge: the crime zone holds exactly two people and David and Fabian are already there, and with Elena that would be more than two; Elena cannot be in the Service Corridor: the crime zone holds exactly two people and Connie and Gloria are already there, and with Elena that would be more than two; row 5 belongs to Connie; nobody else can occupy column A, so it must be Elena. Only A6 is left.
- • Fabian: was in the Bar Lounge; column F belongs to Connie; row 1 belongs to David; column E belongs to Gloria; nobody else can occupy column D, so it must be Fabian; row 4 already belongs to Bianca; row 3 belongs to Gloria. Only D2 is left.
- • Gloria: was in the Service Corridor; column G belongs to Angela; row 5 belongs to Connie; column F belongs to Connie; row 4 already belongs to Bianca. Only E3 is left.
- That already places Angela at G7, Bianca at B4, Connie at F5, David at C1, Elena at A6, Fabian at D2 and Gloria at E3.
- With all seven placed, the only people in the Lobby are Elena and Bianca: Bianca was alone with the victim.
