Most singular case, Watson

The first puzzle of the season was based on a Sherlock Holmes case, "The Adventure of the Speckled Band" by Sir Arthur Conan Doyle.

Some oddities here. If the room is that of Dr. Grimsby Roylott, as the top hat, safe, and pipe suggest, then why is there a woman's shawl on his chair? Also, what is that pair of spectacles doing on the floor? And why is the lantern in this room? Roylott's step-daughter Helen was the one who used it to signal to Holmes and Watson when the coast was clear.

But that's just the picture. An even stranger anomaly is the missing piece. In all my years of puzzling, I've never seen this before. Not only that but an extra piece, which is an almost duplicate of another piece, as shown below. What exactly happened at the jigsaw puzzle factory?  A comedian? A careless packer? A disgruntled employee? 'Tis a mystery indeed.