Sleuthic

The Black Files · October 7, 2026 · Difficulty: Investigator

Black File #118 — SolutionChain of Custody

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The case

Gwen Thornton, parent, was found dead at Brookfield High School at 10:45 PM. Seven people were at the scene. Exactly one of them was alone with Gwen in the same zone.

The evidence (9 clues)
  1. Cynthia was sitting on the sofa.
  2. Diane was standing on the stairs.
  3. Bruce was standing on the stairs.
  4. Florence was standing on the floor.
  5. Alicia was the southernmost person at the scene.
  6. Elliot and Florence were in the same zone.
  7. Bruce was the northernmost person at the scene.
  8. Cynthia was the westernmost person at the scene.
  9. Florence was the easternmost person at the scene.

The answer

The killer: Alicia Farrell, alone with Gwen Thornton in the Faculty Lounge.

Fixing rows and columns from the extreme-position clues cascades through the board and leaves Alicia alone with Gwen in the Faculty Lounge.

Step-by-step deduction

  1. Before placing anyone, each clue eliminates cells:
  2. • Alicia: was the southernmost person of all, and since there is one person per row somebody occupies row 7: that is Alicia; column E already belongs to Bruce; column A belongs to Cynthia; column G belongs to Florence; column F belongs to Elliot. Only B7 is left.
  3. • Bruce: was on the stairs; was the northernmost person of all, and since there is one person per row somebody occupies row 1: that is Bruce. Only E1 is left.
  4. • Cynthia: was sitting on the sofa; was the westernmost person of all, and since there is one person per column somebody occupies column A: that is Cynthia; row 5 belongs to Diane. Only A2 is left.
  5. • Diane: was on the stairs; row 1 already belongs to Bruce; column E already belongs to Bruce; row 7 belongs to Alicia; column A belongs to Cynthia. Only C5 is left.
  6. • Elliot: row 1 already belongs to Bruce; column E already belongs to Bruce; row 7 belongs to Alicia; column A belongs to Cynthia; row 5 belongs to Diane; column C belongs to Diane; column G belongs to Florence; was in the same zone as Florence, and Florence can only be in the Principal's Office; row 2 already belongs to Cynthia; row 3 belongs to Florence. Only F4 is left.
  7. • Florence: was standing on the floor; was the easternmost person of all, and since there is one person per column somebody occupies column G: that is Florence; row 7 belongs to Alicia; row 2 already belongs to Cynthia. Only G3 is left.
  8. • Gwen: row 1 already belongs to Bruce; column E already belongs to Bruce; row 7 belongs to Alicia; column A belongs to Cynthia; row 5 belongs to Diane; column C belongs to Diane; column G belongs to Florence; Gwen cannot be in the Chemistry Lab: the crime zone holds exactly two people and Bruce and Cynthia are already there, and with Gwen that would be more than two; Gwen cannot be in the Principal's Office: the crime zone holds exactly two people and Elliot and Florence are already there, and with Gwen that would be more than two; column F belongs to Elliot; nobody else can occupy row 6, so it must be Gwen; nobody else can occupy column D, so it must be Gwen. Only D6 is left.
  9. That already places Bruce at E1, Cynthia at A2, Diane at C5, Alicia at B7, Elliot at F4, Florence at G3 and Gwen at D6.
  10. With all seven placed, the only people in the Faculty Lounge are Gwen and Alicia: Alicia was alone with the victim.
Solved map of Black File #118: Alicia B7, Bruce E1, Cynthia A2, Diane C5, Elliot F4, Florence G3, Gwen D6
The solved map: Alicia B7, Bruce E1, Cynthia A2, Diane C5, Elliot F4, Florence G3, Gwen D6.

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