Sleuthic

The Black Files · October 3, 2026 · Difficulty: Investigator

Black File #114 — SolutionClean Room

Missed the case? Play Black File #114 →

The case

Colin Pruitt, grant administrator, was found dead at Hartwell Research Lab at 6:05 AM. Seven people were at the scene. Exactly one of them was alone with Colin in the same zone.

The evidence (10 clues)
  1. Gail was standing on the stairs.
  2. Esther was standing on the floor.
  3. Daniel was in the Break Room.
  4. Daniel was sitting in a chair.
  5. Gail was in the Sample Vault.
  6. Benjamin was standing on the stairs.
  7. Benjamin was the southernmost person at the scene.
  8. Esther was the northernmost person at the scene.
  9. Fiona was the easternmost person at the scene.
  10. Alicia was the westernmost person at the scene.

The answer

The killer: Fiona Sokolov, alone with Colin Pruitt in the Bench Area.

Fixing rows and columns from the extreme-position clues cascades through the board and leaves Fiona alone with Colin in the Bench Area.

Step-by-step deduction

  1. Before placing anyone, each clue eliminates cells:
  2. • Alicia: was the westernmost person of all, and since there is one person per column somebody occupies column A: that is Alicia; row 7 belongs to Benjamin; row 1 belongs to Esther; row 5 belongs to Gail. Only A2 is left.
  3. • Benjamin: was on the stairs; was the southernmost person of all, and since there is one person per row somebody occupies row 7: that is Benjamin; column C belongs to Gail. Only B7 is left.
  4. • Colin: Colin cannot be in the Break Room: the crime zone holds exactly two people and Daniel and Esther are already there, and with Colin that would be more than two; column A belongs to Alicia; row 7 belongs to Benjamin; row 1 belongs to Esther; column G belongs to Fiona; row 5 belongs to Gail; column C belongs to Gail; nobody else can occupy column E, so it must be Colin. Only E4 is left.
  5. • Daniel: was in the Break Room; was sitting in a chair; row 1 belongs to Esther. Only F3 is left.
  6. • Esther: 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 Esther; column F already belongs to Daniel. Only D1 is left.
  7. • Fiona: was the easternmost person of all, and since there is one person per column somebody occupies column G: that is Fiona; row 7 belongs to Benjamin; row 1 belongs to Esther; row 2 already belongs to Alicia; row 4 already belongs to Colin; row 3 already belongs to Daniel. Only G6 is left.
  8. • Gail: was on the stairs; was in the Sample Vault; column A belongs to Alicia. Only C5 is left.
  9. That already places Alicia at A2, Benjamin at B7, Colin at E4, Daniel at F3, Gail at C5, Esther at D1 and Fiona at G6.
  10. With all seven placed, the only people in the Bench Area are Colin and Fiona: Fiona was alone with the victim.
Solved map of Black File #114: Alicia A2, Benjamin B7, Colin E4, Daniel F3, Esther D1, Fiona G6, Gail C5
The solved map: Alicia A2, Benjamin B7, Colin E4, Daniel F3, Esther D1, Fiona G6, Gail C5.

Play today's case →