The Mysterious Affair at Styles

A "man of method" was, in Poirot's estimation, the highest praise that could be bestowed on any individual.

I felt that my friend was not what he had been as he rambled on disconnectedly: "There were no stamps in his desk, but there might have been, eh, mon ami? There might have been? Yes"--his eyes wandered round the room--"this boudoir has nothing more to tell us. It did not yield much. Only this."

He pulled a crumpled envelope out of his pocket, and tossed it over to me. It was rather a curious document. A plain, dirty looking old envelope with a few words scrawled across it, apparently at random. The following is a facsimile of it.