Baker Street Saturday - More Holmes Haikus

It's light fare today in Baker Street:

(Haikus - 17 syllables, 5/7/5)

Can you identify which stories the following refer to?

Sherlock Holmes Haikus

Things we send by post.
What is in the cardboard box?
Don't ask - really, don't.



A killer kills Holmes?
Sumatra River Fever.
Watson overhears.

These Sherlock Holmes haikus are too easy for guessing which story inspired them:
http://jenniferoberth.blogspot.com/2011/07/baker-street-saturday-haikus.html

Hope you enjoy!