That Little Square Box

That Little Square Box is a short story written by Arthur Conan Doyle first published in London Society magazine in december 1881, signed as A. C. D.
Mr. Hammond, who is travelling on the American steamer 'The Spartan' is suspicious about two passengers after having witnessed their conversation on the deck. They were talking about a secret square box, a mechanism and the fact that the world will soon hear of it...