The answer to the riddle -- whosawit?

[pippin_999]

No: HPFGUIDX 129774

--- In HPforGrownups at yahoogroups.com, "Jen Reese" <stevejjen at e...>
wrote:

> Any way to resolve this SK problem? I can't imagine Snape showing
up  at GH and James coming to any other conclusion but that Peter
betrayed  them.
> 


Pippin:
Sure. Snape shows up at the Potters'  _before_ the spell is
activated. 
Remember the spell takes time to set up and there was a  period of 
debate about who the SK should be; Dumbledore offered to do it 
but James insisted on Sirius. 

So Snape, at great personal risk, shows up on James's
doorstep and says, "Don't choose Sirius, he's the spy." James tells 
him to get lost. This accounts for Snape's furious refusal to
consider that there could have been a switch. That last thing he
wants to believe is that James did  listen to him after all, made 
Peter the secret-keeper, and died for it.

As for how Dumbledore knew what went down at GH, I have a 
feeling that Nicholas Flammel  (who better?) instructed both DD 
and Lily in ancient magic and that Dumbledore knew that
Lily was prepared to die to save Harry. Perhaps those little
silver instruments were able to confirm the blood protection.

Pippin