Sleuthic

The Black Files · November 12, 2026 · Difficulty: Investigator

Black File #154 — SolutionThe Stairwell

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The case

Fiona Whitaker, commuter, was found dead at Fifth Street Parking Garage at 11:15 PM. Seven people were at the scene. Exactly one of them was alone with Fiona in the same zone.

The evidence (8 clues)
  1. Esther was sitting on a sofa.
  2. David was in the Attendant Booth.
  3. Benjamin was sitting on a sofa.
  4. Aaron and Carla were in the same zone.
  5. Aaron was the westernmost person at the scene.
  6. Gail was the easternmost person at the scene.
  7. Benjamin and Esther were in the same zone.
  8. Esther was the northernmost person at the scene.

The answer

The killer: Gail Bishop, alone with Fiona Whitaker in the Level One.

Fixing rows and columns from the extreme-position clues cascades through the board and leaves Gail alone with Fiona in Level One.

Step-by-step deduction

  1. Before placing anyone, each clue eliminates cells:
  2. • Aaron: was the westernmost person of all, and since there is one person per column somebody occupies column A: that is Aaron; row 1 already belongs to Esther; row 2 already belongs to Benjamin; was in the same zone as Carla, and Carla can only be in the Stairwell Lobby; row 4 already belongs to Carla. Only A3 is left.
  3. • Benjamin: was sitting on the sofa; row 1 already belongs to Esther; column D already belongs to Esther; column G belongs to Gail; was in the same zone as Esther, and Esther can only be in the Entrance Ramp. Only C2 is left.
  4. • Carla: row 1 already belongs to Esther; column D already belongs to Esther; column A belongs to Aaron; column G belongs to Gail; was in the same zone as Aaron, and Aaron can only be in the Attendant Booth or the Stairwell Lobby; row 2 already belongs to Benjamin; column C already belongs to Benjamin; column B belongs to David. Only E4 is left.
  5. • David: was in the Attendant Booth; column D already belongs to Esther; column A belongs to Aaron; column C already belongs to Benjamin; row 5 belongs to Gail. Only B6 is left.
  6. • Esther: 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 Esther. Only D1 is left.
  7. • Fiona: row 1 already belongs to Esther; column D already belongs to Esther; column A belongs to Aaron; column G belongs to Gail; Fiona cannot be in the Entrance Ramp: the crime zone holds exactly two people and Benjamin and Esther are already there, and with Fiona that would be more than two; row 2 already belongs to Benjamin; column C already belongs to Benjamin; column B belongs to David; nobody else can occupy column F, so it must be Fiona; row 4 already belongs to Carla; row 5 belongs to Gail; nobody else can occupy row 7, so it must be Fiona. Only F7 is left.
  8. • Gail: was the easternmost person of all, and since there is one person per column somebody occupies column G: that is Gail; only Fiona and the killer were in the crime zone (Level One) and only Fiona and Gail can be there; row 4 already belongs to Carla. Only G5 is left.
  9. That already places Esther at D1, Benjamin at C2, Carla at E4, Aaron at A3, David at B6, Fiona at F7 and Gail at G5.
  10. With all seven placed, the only people in Level One are Fiona and Gail: Gail was alone with the victim.
Solved map of Black File #154: Aaron A3, Benjamin C2, Carla E4, David B6, Esther D1, Fiona F7, Gail G5
The solved map: Aaron A3, Benjamin C2, Carla E4, David B6, Esther D1, Fiona F7, Gail G5.

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