All the brains in the world cannot make up for the lack of an elementary knowledge of the place and the characters themselves.

It stands to reason that no strange detective could form as good an opinion as to which of the members of your household would be most likely to steal a piece of jewelry as you could yourself.

Yet the old-fashioned Sherlock knew and knows it all.
One of the best illustrations of the practical necessity of some first-hand knowledge is that afforded by the recovery of a diamond necklace belonging to the wife of a gentleman in a Connecticut town.
The facts that are given here are absolutely accurate.

The gentleman in question was a retired business man of some means who lived not far from the town and who made frequent visits to New York City.

He had made his wife a present of a fifteen thousand-dollar diamond necklace, which she kept in a box in a locked trunk in her bedroom.