The Memoirs of Sherlock Holmes - The "Gloria Scott"
This is Holmes' first case, he shows Watson a note:
"The supply of game for London is going to steadily up [it ran]. Head-keeper Hudson, we believe, has been now told to receive all orders for fly-paper and for preservation of your hen-pheasant's life."
The client was his only friend in college, Victor Trevor. Holmes was invited to vacation with Victor in his home in Birmingham. He uses his deduction skills to wow and shock Sr Trevor causing him to be cautious around Holmes.
On the day that Holmes left, a drunken sailor comes to visit. Sr Trevor went above and beyond to appease him.
Two months later, Victor goes to see Holmes to tell him that the sailor, Hudson, is "the devil." He drinks and acts like he owns the place. And his father has fallen ill and is in his deathbed.
Result: Sr Trevor died and left his son a letter with the story. His real name is James Armitage, he was being transported on Gloria Scott as a convict. They overthrew the crew and just as they were escaping from the ship it blew up. He and his friend Evans changed their names and both prospered. Hudson, the only survivor of the explosion did not prosper. He went around blackmailing all the escapees.
The real message behind the note was actually this:
"The supply of game for London is going steadily up. Head-keeper Hudson, we believe, has been now told to receive all orders for fly-paper and for preservation of your hen-pheasant's life."