The Cullinan Diamond (The Adventures of the Elderly Sherlock Holmes, Episode 18)

It was a Friday evening in November. Holmes and Watson were summoned by Inspector Wolfford to a crime scene. But it wasn't an ordinary robbery, as Holmes immediately established, for one detail didn't fit the picture. Why were the victim's shoes stolen but his expensive wristwatch left behind? When an unusual bank robbery takes place the following day and there's another corpse with the same murder weapon, Holmes is certain of a connection between the two murder cases. But what links the two victims together? And finally, the question remains: what the devil has Dr John Watson got himself mixed up in this time?