'The Adventure of The Second Stain' is a Sherlock Holmes short story written by Sir Arthur Conan Doyle, best known for his novel 'The Hound of the Baskervilles.' It is one of 13 stories in the cycle collected as 'The Return of Sherlock Holmes.' Doyle ranked 'The Adventure of the Second Stain' eighth in a list of his twelve favorite Sherlock Holmes short stories.

Lord Bellinger, the Prime Minister, and Trelawney Hope, the Secretary for European Affairs, come to see Sherlock Holmes about the matter of a document stolen from Hope's dispatch box which he kept at home in Whitehall Terrace when not at work. A very serious matter. If divulged, this document could bring about very dire consequences for all of Europe, even war. They are loath to tell Holmes at first the exact nature of the document, but eventually feel that they must tell him that it was a rather injudicious letter from a foreign potentate. It disappeared from the dispatch box one evening when Hope was out for four hours. No-one in the house knew about it, not even the Secretary's wife with whom he does not discuss his work.