The Adventure of the Second Stain recap

Prime Minister Lord Bellinger and European secretary Trelawney Hope ask Sherlock Holmes to recover a stolen letter whose publication could cause an international crisis. The disappearance coincides with the murder of suspected agent Eduardo Lucas. A bloodstained carpet at Lucas's house has been shifted, revealing a hiding place beneath the floor. Holmes traces the second visitor to Hope's wife, Lady Hilda. Lucas had blackmailed her over a compromising letter from before her marriage and forced her to steal the state paper. Lucas's jealous wife killed him while Lady Hilda was concealed in the room, allowing her to see where he hid the document and recover it later. Holmes persuades Lady Hilda to give him the paper and has her replace it in her husband's dispatch box. When Hope searches again, he finds it. Holmes preserves Lady Hilda's secret and lets the government believe the dangerous document had never left its keeper's possession.

Prime Minister Lord Bellinger and the secretary for European affairs, Trelawney Hope, visit Sherlock Holmes about a letter stolen from Hope's locked dispatch box. Written by a foreign ruler, it could provoke war if published. Only a few people knew Hope possessed it, and the officials demand absolute secrecy. After they leave, Lady Hilda Hope privately asks Holmes about the danger while claiming ignorance of the document itself. Holmes considers several international agents who might exploit it. One, Eduardo Lucas, was stabbed at his London home on the night of the theft. The murder initially appears domestic when the police learn that Lucas lived under another identity in Paris and was killed by his jealous wife, Madame Fournaye. Lestrade later draws Holmes's attention to a bloodstain on Lucas's carpet that does not align with the stain on the boards. The carpet was moved after the murder, exposing a concealed space beneath the floor. Holmes confronts Lady Hilda. She admits that Lucas blackmailed her with an indiscreet premarital letter and demanded the state paper in exchange. Hidden during Lucas's fatal confrontation with his wife, she saw him conceal the stolen document and later returned to recover it, shifting the carpet. Holmes makes her surrender the letter and replace it in her husband's dispatch box. Hope then finds it during a new search, allowing Holmes to protect Lady Hilda and resolve the international danger without revealing the truth to his official clients.

Holmes identifies Lady Hilda as the person who removed the state letter from her husband's dispatch box. Eduardo Lucas had obtained an indiscreet letter she wrote before her marriage and threatened to expose it unless she brought him the diplomatic paper. While she was delivering it, Lucas's jealous wife arrived and killed him; hidden nearby, Lady Hilda saw Lucas place the paper beneath a loose section of floor. She later returned and shifted the bloodstained carpet to retrieve it, producing the mismatch that attracted Lestrade's attention. Holmes compels her to surrender the paper but protects her marriage and reputation. Following his instructions, she replaces it in the dispatch box before Trelawney Hope and Lord Bellinger return. Holmes then invites Hope to search again. The letter is found, and the prime minister concludes that it was never stolen. Holmes leaves both officials unaware of Lady Hilda's theft, the blackmail, and his intervention.