Snape knew about the passageway

[judyserenity]

No: HPFGUIDX 34788

Carrie said:
> ...I see many complaints about Lupin not informing Dumbledore 
> about the Passageway at the whomping Willow, but all this debate 
> about Sirius and Snape has me thinking that Snape also knew about 
> the route.  He also knew that Sirius knew and that it led right on 
> to Hogwart's grounds.  So, what is Snape's excuse? 

Knowing about the Whomping Willow passageway is not the problem.  In 
fact, probably the whole Hogwarts staff knows about the passageway -- 
Pomfrey used to take Lupin there, and Dumbledore was the one who 
arranged to have it built.  And Dumbledore knows that Sirius knows 
about the passge, because of the whole infamous Prank thing back when 
Sirius and Snape were students; Dumbledore knows that Sirius sent 
Snape down that passageway.  There's no reason for Snape to tell 
Dumbledore any of this; Dumbledore knows it already. 

No, the problem is that only Lupin knows that Sirius is an animagus.  
This is the secret that Lupin has been keeping from Dumbledore.  
Sirius has been sneaking around the Hogwarts grounds in dog form, and 
only Lupin knows he can do that. 

By the way, there are also a bunch of other passageways that Lupin 
knows about (such as the one that goes from the one-eyed witch to 
Honeydukes.)  We don't know if Dumbledore is aware of these 
passageways; Snape clearly is not, as he examines the one-eyed witch 
and doesn't discover its secret.