Sleuthic

The Black Files · October 17, 2026 · Difficulty: Senior Detective

Black File #128 — SolutionQuarter Past

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The case

Colin Sullivan, estate executor, was found dead at SecureBox Storage Facility at 10:45 PM. Seven people were at the scene. Exactly one of them was alone with Colin in the same zone.

The evidence (9 clues)
  1. Edith was sitting on a sofa.
  2. Dennis was sitting in a chair.
  3. Gina was sitting on a sofa.
  4. Brian was sitting on a sofa.
  5. Franklin was the westernmost person at the scene.
  6. Amber and Dennis were in the same zone.
  7. Amber was the southernmost person at the scene.
  8. Brian and Gina were in the same zone.
  9. Gina was the northernmost person at the scene.

The answer

The killer: Edith Nakamura, alone with Colin Sullivan in the Unit Corridor.

Nothing is forced until you test Dennis at E5 or G5: every wrong cell leaves someone with no possible cell. With Dennis at E5 the rest cascades and leaves Edith alone with Colin in Unit Corridor.

Step-by-step deduction

  1. Before placing anyone, each clue eliminates cells:
  2. • Brian: was sitting on the sofa; row 1 already belongs to Gina; column B already belongs to Gina; column A belongs to Franklin; was in the same zone as Gina, and Gina can only be in Unit 118. Only D3 is left.
  3. • Gina: 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 Gina. Only B1 is left.
  4. • Dennis: was sitting in a chair; column B already belongs to Gina; row 7 belongs to Amber; column A belongs to Franklin; was in the same zone as Amber, and Amber can only be in the Front Office or Unit Corridor. Remaining: E5 and G5.
  5. • Franklin: was the westernmost person of all, and since there is one person per column somebody occupies column A: that is Franklin; row 7 belongs to Amber; row 3 already belongs to Brian; row 5 belongs to Dennis. Remaining: A2 and A4.
  6. • Colin: row 1 already belongs to Gina; column B already belongs to Gina; row 7 belongs to Amber; column A belongs to Franklin; nobody else can occupy row 6, so it must be Colin; column D already belongs to Brian. Remaining: C6, E6 and G6.
  7. • Edith: was sitting on the sofa; row 1 already belongs to Gina; column B already belongs to Gina; column A belongs to Franklin; row 3 already belongs to Brian; column D already belongs to Brian. Remaining: F2, G2 and F4.
  8. • Amber: was the southernmost person of all, and since there is one person per row somebody occupies row 7: that is Amber; column B already belongs to Gina; column A belongs to Franklin; column D already belongs to Brian. Remaining: C7, E7, F7 and G7.
  9. That already places Gina at B1 and Brian at D3.
  10. At this point no cell is forced. Time to test a hypothesis. Try Dennis, who can only be at E5 or G5.
  11. – Dennis at E5: everything fits: it yields Amber at C7, Colin at G6, Edith at F4 and Franklin at A2.
  12. – Dennis at G5: Amber is left with no possible cell. Impossible.
  13. So Amber goes to C7, Colin goes to G6, Dennis goes to E5, Edith goes to F4 and Franklin goes to A2.
  14. With all seven placed, the only people in Unit Corridor are Colin and Edith: Edith was alone with the victim.
Solved map of Black File #128: Amber C7, Brian D3, Colin G6, Dennis E5, Edith F4, Franklin A2, Gina B1
The solved map: Amber C7, Brian D3, Colin G6, Dennis E5, Edith F4, Franklin A2, Gina B1.

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