The Adventure of the Second Stain

Trelawney Hope, secretary for European Affairs, reaches out to Holmes. A very important letter was stolen from Hope’s safe and he wants Holmes to track it down. The letter’s content was of political importance and the three main suspects of Holmes are international secret agents. However one of them, Eduardo Lucas, was found murdered. Is there some connection between both crimes and will Holmes connect the dots?
"The Adventure of the Second Stain" is a part of "The Return of Sherlock Holmes".

Sir Arthur Conan Doyle (1859-1930) was born in Scotland and studied medicine at the University of Edinburgh. After his studies, he worked as a ship’s surgeon on various boats. During the Second Boer War, he was an army doctor in South Africa. When he came back to the United Kingdom, he opened his own practice and started writing crime books. He is best known for his thrilling stories about the adventures of Sherlock Holmes. He published four novels and more than 50 short-stories starring the detective and Dr Watson, and they play an important role in the history of crime fiction. Other than the Sherlock Holmes series, Doyle wrote around thirty more books, in genres such as science-fiction, fantasy, historical novels, but also poetry, plays, and non-fiction.