"The Adventure of the Second Stain" is a Sherlock Holmes short story by Sir Arthur Conan Doyle, featured in The Return of Sherlock Holmes collection. It was first published in The Strand Magazine in the UK in December 1904 and in Collier's in the US on January 28, 1905. The story involves Holmes being consulted by the Prime Minister and the Secretary of State for European Affairs after a sensitive diplomatic document goes missing, with its disclosure threatening severe political consequences across Europe.