Solution: The Scream Before Dawn at the Grand Hotel

The clues

• 
  RafaelThe bicycle courier.

  He was in the Cloakroom.

• 
  KarimThe family lawyer.

  He was in the top row. He was in the third column from the left.

• 
  TheoThe paperboy.

  He was beside a luggage trolley.

• 
  Clara · VictimThe young reporter.

  The victim. She was alone with the killer.

• 
  JonasThe shy librarian.

  He was on a chair. He was not in the Bar.

• 
  YaraThe young pharmacist.

  She was in the fourth row.

• 
  MateoThe waiter who hears everything.

  He was on an armchair.

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. Last cell left Every other cell is ruled out for Karim, by his testimony or by a row or column already taken. Placed: Karim: row 1, column 3 (Bar); Theo: row 7, column 5 (Restaurant).
2. Pinned suspects Yara can only be in the fourth row, so nobody else can be there.
3. Pinned suspects Mateo can only be in the sixth column from the left, so nobody else can be there.
4. Room counting The victim, Clara, cannot be in the highlighted cells: her room there could not hold exactly one other person. The cells meant: row 2, column 1; row 2, column 7; row 3, column 1; row 3, column 7; row 6, column 7.
5. Shared rows and columns Rafael and Jonas can only be in the second column from the left and the right column between them, so nobody else can be in those columns.
6. The only one who fits Only Jonas can still reach the third row, so he must be there. Placed: Jonas: row 3, column 2 (Roof Terrace).
7. Room counting The victim, Clara, cannot be in the highlighted cells: her room there could not hold exactly one other person. The cells meant: row 5, column 1. Placed: Clara: row 2, column 4 (Bar); Yara: row 4, column 1 (Roof Terrace); Mateo: row 6, column 6 (Cloakroom); Rafael: row 5, column 7 (Cloakroom).