Solution: The Telephone Call After Dinner at the Museum

The clues

• 
  RafaelThe bicycle courier.

  He was on a chair.

• 
  WalterThe estate’s groundskeeper.

  He was on a stool.

• 
  HugoThe retired colonel.

  He was beside a bookshelf.

• 
  YaraThe young pharmacist.

• 
  Theo · VictimThe paperboy.

  The victim. He was alone with the killer. He was on a rug.

• 
  OscarThe antiques dealer.

  He was in the Courtyard with another man.

• 
  NoraThe village doctor.

  She was on a stool.

Step by step

The order our solver finds. Each step uses only the clues and what the steps before it proved, and its heading links to the technique.

1. Follow it to a contradiction If Theo were in the highlighted cell, Oscar would have no cell left. So he is not there. The cells meant: row 2, column 5. Placed: Theo: row 3, column 7 (Lobby).
2. Shared rows and columns Walter and Nora can only be in the fourth row and the bottom row between them, so nobody else can be in those rows.
3. Follow it to a contradiction If Rafael were in the highlighted cell, Oscar would have no cell left. So he is not there. The cells meant: row 1, column 1.
4. Pinned suspects Rafael can only be in the fifth column from the left, so nobody else can be there.
5. Follow it to a contradiction If Rafael were in the highlighted cell, Theo would have no cell left. So he is not there. The cells meant: row 1, column 5. Placed: Rafael: row 5, column 5 (Lobby).
6. Pinned suspects Oscar can only be in the sixth row, so nobody else can be there.
7. Room counting Oscar cannot be in the highlighted cells: he could not be there with exactly one other man. The cells meant: row 6, column 1. Placed: Oscar: row 6, column 2 (Courtyard).
8. Room counting Oscar was in the Courtyard with exactly one other man. Only Walter can still get there. Placed: Walter: row 4, column 1 (Courtyard); Hugo: row 1, column 4 (Gift Shop); Yara: row 2, column 6 (Gallery); Nora: row 7, column 3 (Workshop).