In the novel The Sittaford Mystery, Edgar Rosenkraun is an American publisher. The novelist Martin Dering used Rosenkraun as an alibi, claiming that he was with him the whole afternoon on the day of the murder of Captain Trevelyan.
By the time Inspector Narracott questioned Dering in detail about this alibi, Rosenkraun had departed England for New York on board the liner Gargantua. When Narracott wanted to send a telegram to Rosenkraun to confirm Dering's alibi, Dering requested to be the one to draft the telegram and have it sent in his name, and for the reply to be delivered to a private address. Narracott agreed to this rather unusual request. Soon the reply from Rosenbraun came, to Narracott's private Exeter address, confirming that he had been with Dering the whole afternoon.
But the suspicious Narracott decided to send a second telegram to Rosenkraun. In this, he identified himself as a divisional inspector conducting a murder investigation and asked Rosenkraun to reconfirm the alibi. This time, Rosenkraun's reply "showed agitation and a reckless disregard for expense." He stated that he did not know it was a criminal case. He did not see Dering at all on the Friday concerned. He initially agreed to alibi Dering as a favour from one friend to another because he believed Dering's wife was having him watched for divorce proceedings.