Surely, Charles Clemency must be the murderer? After all, he is the only actual suspect found in the locked bedchamber next to the still, graceful body of his lady wife.
Inspector Lestrade is justifiably proud of himself for solving a case without the assistance from you-know-who. The compelling evidence confirms that there is nothing irregular about this investigation, and that Charles is clearly as guilty as sin.
So, why is Holmes suddenly taking a keen interest in the case..?