This is a followup question to my own answer on another Sherlock question regarding the Season 3 finale "The Last Vow", from which I will shamelessly copy contents below.
During their visit in Bakerstreet, Magnussen lists Sherlock's weaknesses (as we find out later) in his mind.
There are only six points being listed here (and infinitely scrolled, likely for effect, to indicate that there are more than usual):
- Irene Adler (see File)
- Jim Moriarty (see File)
- Redbeard (see File)
- Hounds of the Baskerville
- John Watson
While I don't think all of them make sense as a pressure point on Sherlock, I at least understand what they are and why Magnussen might think that he could use those topics against Sherlock.
That is, all of them except one: "Hounds of the Baskerville"
What does "Hounds of the Baskerville" mean in this context, and why does Magnussen think he can use this to blackmail Sherlock?
If I remember the plot of the Baskerville episode correctly, there never really were any hounds and it was instead some kind of experimental biochemical weapon that was produced by a secret government/military facility. I don't see how that could be used against Sherlock, or anything else that Sherlock did during that case that could be used to blackmail him. He infiltrated the secret complex with his brother's ID, but that was discovered, so not really blackmail material.
Is there any indication in the show that explains this point on Magnussen's list?