Sleuthic

The Black Files · November 1, 2026 · Difficulty: Cadet

Black File #143 — SolutionPaper Trail

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The case

Grace Doyle, health inspector, was found dead at Marlow's Restaurant at 8:40 PM. Seven people were at the scene. Exactly one of them was alone with Grace in the same zone.

The evidence (10 clues)
  1. Anthony was sitting in a chair.
  2. Claire was sitting on a sofa.
  3. Frank was standing on stairs.
  4. Bonnie was standing on stairs.
  5. Ethan was standing on the floor.
  6. Denise was in the Dining Room.
  7. Anthony was the easternmost person at the scene.
  8. Ethan was the northernmost person at the scene.
  9. Bonnie and Frank were in the same zone.
  10. Frank was the westernmost person at the scene.

The answer

The killer: Claire Marsh, alone with Grace Doyle in the Back Alley.

Fixing rows and columns from the extreme-position clues cascades through the board and leaves Claire alone with Grace in the Back Alley.

Step-by-step deduction

  1. Before placing anyone, each clue eliminates cells:
  2. • Anthony: was sitting in a chair; was the easternmost person of all, and since there is one person per column somebody occupies column G: that is Anthony; row 3 belongs to Denise. Only G5 is left.
  3. • Bonnie: was on the stairs; column G belongs to Anthony; column A belongs to Frank; was in the same zone as Frank, and Frank can only be in the Bar or the Back Alley; row 2 already belongs to Frank; row 3 belongs to Denise. Only B4 is left.
  4. • Claire: was sitting on the sofa; column G belongs to Anthony; row 1 belongs to Ethan; row 2 already belongs to Frank; nobody else can occupy row 7, so it must be Claire. Only C7 is left.
  5. • Denise: was in the Dining Room; column G belongs to Anthony; row 1 belongs to Ethan; row 2 already belongs to Frank; nobody else can occupy column E, so it must be Denise. Only E3 is left.
  6. • Ethan: was standing on the floor; was the northernmost person of all, and since there is one person per row somebody occupies row 1: that is Ethan; column A belongs to Frank; nobody else can occupy column F, so it must be Ethan. Only F1 is left.
  7. • Frank: was on the stairs; was the westernmost person of all, and since there is one person per column somebody occupies column A: that is Frank; was in the same zone as Bonnie, and Bonnie can only be in the Bar. Only A2 is left.
  8. • Grace: column G belongs to Anthony; row 1 belongs to Ethan; column A belongs to Frank; Grace cannot be in the Bar: the crime zone holds exactly two people and Bonnie and Frank are already there, and with Grace that would be more than two; row 2 already belongs to Frank; row 3 belongs to Denise; nobody else can occupy row 6, so it must be Grace; nobody else can occupy column D, so it must be Grace. Only D6 is left.
  9. That already places Frank at A2, Anthony at G5, Bonnie at B4, Claire at C7, Denise at E3, Ethan at F1 and Grace at D6.
  10. With all seven placed, the only people in the Back Alley are Grace and Claire: Claire was alone with the victim.
Solved map of Black File #143: Anthony G5, Bonnie B4, Claire C7, Denise E3, Ethan F1, Frank A2, Grace D6
The solved map: Anthony G5, Bonnie B4, Claire C7, Denise E3, Ethan F1, Frank A2, Grace D6.

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