Solution: The Whisper Before Dawn aboard the Ocean Liner

The clues

• 
  WalterThe estate’s groundskeeper.

  He was on a bench. He was in the Engine Room.

• 
  NoraThe village doctor.

  She was on a bench. She was in the Galley.

• 
  Quentin · VictimThe butler of forty years.

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

• 
  RafaelThe bicycle courier.

  He was in the third row.

• 
  PaulaThe opera singer between engagements.

  She was beside a chair. She was alone in the room.

• 
  ZoeThe tattoo artist.

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 Walter, by his testimony or by a row or column already taken. Placed: Walter: row 1, column 4 (Engine Room); Nora: row 4, column 6 (Galley).
2. Pinned suspects Rafael can only be in the third row, so nobody else can be there.
3. Pinned suspects Paula can only be in the fifth column from the left, so nobody else can be there.
4. Room counting Paula cannot be in the highlighted cells: she would not be alone there. The cells meant: row 2, column 5. Placed: Paula: row 6, column 5 (Lounge).
5. Room counting The victim, Quentin, cannot be in the highlighted cells: his room there could not hold exactly one other person. The cells meant: row 5, column 1. Placed: Quentin: row 2, column 2 (Chart Room); Zoe: row 5, column 1 (Cargo Hold); Rafael: row 3, column 3 (Chart Room).