The Black Files · October 25, 2026 · Difficulty: Elite

Black File #136 — SolutionAfter Hours

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The case

Gregory Reyes, janitor, was found dead at Brookfield High School at 6:05 AM. Seven people were at the scene. Exactly one of them was alone with Gregory in the same zone.

The answer

The killer: Colin Vaughn, alone with Gregory Reyes in the Chemistry Lab.

Nothing is forced until you test Alicia at D1, E1, F1, G1, D2, E2, G2, D3, E3, E4, G4, D5 or G5: every wrong cell leaves someone with no possible cell. With Alicia at G2 the rest cascades and leaves Colin alone with Gregory in the Chemistry Lab.

Step-by-step deduction

1. Before placing anyone, each clue eliminates cells:
2. • Colin: was sitting in a chair; Franklin was farther west than Colin, and Franklin is at least at column C; Franklin was farther north than Colin, and Franklin is at least at row 2. Remaining: D3, G5, E6 and G6.
3. • Evelyn: was sitting in a chair; was farther west than Franklin, and Franklin is no farther than column F; column A belongs to Bridget. Remaining: E2, D3, C4, B6 and E6.
4. • Bridget: was the westernmost person of all, and since there is one person per column somebody occupies column A: that is Bridget. Remaining: A1, A3, A4, A5, A6 and A7.
5. • Still wide open: Franklin (11), Alicia (13), Deborah (17) and Gregory (34) possible cells; they close as the others are placed.
6. At this point no cell is forced. Time to test a hypothesis. Try Alicia, who can only be at D1, E1, F1, G1, D2, E2, G2, D3, E3, E4, G4, D5 or G5.
7. – Alicia at D1: forces Evelyn at B6, and then Deborah is left with no possible cell. Impossible.
8. – Alicia at E1: only Gregory could be in the Chemistry Lab, but there were exactly 2 people in the Chemistry Lab. Impossible.
9. – Alicia at F1: forces Colin at E6, and then only Colin could be in the Chemistry Lab, but there were exactly 2 people in the Chemistry Lab. Impossible.
10. – Alicia at G1: Alicia is left with no possible cell. Impossible.
11. – Alicia at D2: forces Evelyn at B6, and then only nobody could be in the Chemistry Lab, but there were exactly 2 people in the Chemistry Lab. Impossible.
12. – Alicia at E2: forces Colin at G6, and then Gregory is left with no possible cell. Impossible.
13. – Alicia at G2: everything fits: it yields Colin at E6, Evelyn at C4, Gregory at F5, Bridget at A7, Deborah at B1 and Franklin at D3.
14. – Alicia at D3: forces Evelyn at B6, and then only nobody could be in the Chemistry Lab, but there were exactly 2 people in the Chemistry Lab. Impossible.
15. – Alicia at E3: forces Colin at G6, and then Gregory is left with no possible cell. Impossible.
16. – Alicia at E4: forces Evelyn at B6, and then only Gregory could be in the Chemistry Lab, but there were exactly 2 people in the Chemistry Lab. Impossible.
17. – Alicia at G4: forces Evelyn at B6, and then only Gregory could be in the Chemistry Lab, but there were exactly 2 people in the Chemistry Lab. Impossible.
18. – Alicia at D5: Evelyn is left with no possible cell. Impossible.
19. – Alicia at G5: forces Colin at E6, and then Gregory is left with no possible cell. Impossible.
20. So Alicia goes to G2, Colin goes to E6, Evelyn goes to C4, Gregory goes to F5, Bridget goes to A7, Deborah goes to B1 and Franklin goes to D3.
21. With all seven placed, the only people in the Chemistry Lab are Gregory and Colin: Colin was alone with the victim.

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