Sleuthic

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

Black File #104 — SolutionThe Last Witness

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The case

Bianca Ibarra, food critic, was found dead at Marlow's Restaurant at 8:40 PM. Seven people were at the scene. Exactly one of them was alone with Bianca in the same zone.

The evidence (10 clues)
  1. Bianca was standing on the stairs.
  2. Gregory was sitting on the sofa.
  3. Florence was in the Back Alley.
  4. Colin was in the Back Alley.
  5. Evelyn was standing on the floor.
  6. Colin was standing on the floor.
  7. Daniel was standing on the floor.
  8. Evelyn was in the Dining Room.
  9. Amber was the northernmost person at the scene.
  10. Gregory was the southernmost person at the scene.

The answer

The killer: Amber Mercer, alone with Bianca Ibarra in the Kitchen.

Fixing rows and columns from the extreme-position clues cascades through the board and leaves Amber alone with Bianca in the Kitchen.

Step-by-step deduction

  1. Before placing anyone, each clue eliminates cells:
  2. • Amber: was the northernmost person of all, and since there is one person per row somebody occupies row 1: that is Amber; nobody else can occupy column A, so it must be Amber. Only A1 is left.
  3. • Bianca: was on the stairs; Bianca cannot be in the Dining Room: the crime zone holds exactly two people and Evelyn and Gregory are already there, and with Bianca that would be more than two; Bianca cannot be in the Back Alley: the crime zone holds exactly two people and Colin and Florence are already there, and with Bianca that would be more than two; row 1 belongs to Amber; nobody else can occupy row 3, so it must be Bianca; nobody else can occupy column B, so it must be Bianca. Only B3 is left.
  4. • Colin: was in the Back Alley; was standing on the floor; row 7 belongs to Gregory; column E already belongs to Florence; column D belongs to Evelyn. Only F6 is left.
  5. • Daniel: was standing on the floor; row 1 belongs to Amber; row 7 belongs to Gregory; nobody else can occupy row 2, so it must be Daniel. Only G2 is left.
  6. • Evelyn: was standing on the floor; was in the Dining Room; row 7 belongs to Gregory; nobody else can occupy row 4, so it must be Evelyn; column G already belongs to Daniel. Only D4 is left.
  7. • Florence: was in the Back Alley; row 7 belongs to Gregory; nobody else can occupy row 5, so it must be Florence. Only E5 is left.
  8. • Gregory: was sitting on the sofa; was the southernmost person of all, and since there is one person per row somebody occupies row 7: that is Gregory; nobody else can occupy column C, so it must be Gregory. Only C7 is left.
  9. That already places Amber at A1, Daniel at G2, Florence at E5, Gregory at C7, Bianca at B3, Colin at F6 and Evelyn at D4.
  10. With all seven placed, the only people in the Kitchen are Bianca and Amber: Amber was alone with the victim.
Solved map of Black File #104: Amber A1, Bianca B3, Colin F6, Daniel G2, Evelyn D4, Florence E5, Gregory C7
The solved map: Amber A1, Bianca B3, Colin F6, Daniel G2, Evelyn D4, Florence E5, Gregory C7.

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