S7E29 - The Adventure of the Second Stain, Part 2

Sherlock Holmes is on a mission to prevent an international incident. The European Secretary has lost an important letter, and Holmes has been entrusted with its safe return. He knows that the disappearance of the letter is tied to the recent murder of Eduardo Lucas, but is stumped on exactly how the two crimes are connected. A visit to the scene of the murder provides him with a vital clue in the form of a second stain on the dead man's carpet. With that second stain, Holmes is able to deduce the truth of the matter, but will he...