The Adventure of the Italian Nobleman — Agatha Christie

Poirot and Hastings are in their rooms with a near neighbour, Dr Hawker, when the medical man's housekeeper arrives with the message that a client, Count Foscatini, has phoned for the doctor, crying out for help. Poirot, Hastings and Hawker rush to Foscatini's flat in Regent's Court. The lift attendant there, unaware of any problems, says that Graves, the Count's man, left half an hour earlier with no indication of anything wrong. The flat is locked but the manager of the building opens it for them. Inside, they find a table set for three people, with the meals finished. The Count is alone and dead!