Lupin was the spy

[snow15145]

No: HPFGUIDX 102786

Was Pettigrew really the Potter's secret keeper? Pettigrew never 
admitted that he was in fact the secret keeper. POA pg. 374 He 
admitted to selling out James and Lily to Voldemort and also to 
passing information for the past year but never did he admit that he 
was secret keeper
 In fact on pg. 369 when Sirius accuses Peter 
specifically of being secret keeper, Peter was muttering 
distractedly, far-fetched and lunacy. I don't think Peter even knew 
of the plan to make him secret keeper until the shrieking shack 
accusations.  

Sirius said pg. 365 " And when I saw their house, destroyed, and 
their bodies
 I realized what Peter must've done
 what I'd done
" 
Here is the clue {what Peter "must've" done; not really sure} it is 
just a guilt ridden assumption on Sirius' part that Peter was in fact 
made secret keeper because he felt he was at fault for persuading 
James and Lily
  No real concrete evidence that Peter was chosen as 
the secret keeper, only Sirius' self-guilt. The secret keeper switch 
had been discussed between James, Lily and Sirius but I don't think 
it went as far as Pettigrew. IMO It would be an assumption on the 
reader's part based entirely on what Sirius thinks happened because 
he suggested Peter instead of himself. Peter was well aware that he 
had been spying and therefore felt guilty of what he had passed onto 
Voldemort. This guilty behavior from Peter allowed us to believe the 
accusation and assumption that Peter was the secret keeper without 
question. But
just because Peter acted guilty didn't make him guilty 
of being the secret keeper.

It is quite possible that Sirius assumed that James switched to Peter 
as secret keeper but that Lily may have questioned Sirius' loyalty, 
to herself and James, because of this last minute request. Lily 
feeling suspicious of Sirius' behavior could have suggested to James 
that they should rethink their position and entrust Lupin instead so 
that Sirius wouldn't know whom the secret keeper actually was incase 
Lily's suspicions were correct about Sirius. (Women can be very 
persuasive...Women willingly trust, where no man would).

Peter was afraid of Sirius all right when he met him in the street 
that day but Peter was also in need of hiding from the DE's that were 
blaming him for the downfall of their master because of information 
that he had told Voldemort. Peter knowing of the incident at Godric's 
Hollow, after the fact, wouldn't necessarily mean that he knew of the 
fidelius charm. Peter could have thought that Sirius was coming after 
him for being a spy for Voldemort; Peter may have thought he had 
caused Lily and James death because of other information he passed to 
Voldemort. Peter (feeling guilty of his betrayal of spying) cornered 
by Sirius, tells the whole street that it was Sirius who killed the 
Potter's and escapes. 

As for the actual secret keeper, I'm guessing Lupin filled the post 
as the one who was ultimately chosen. There are so many things that 
Lupin has said and done that make me question his loyalties
 From 
the "you heard James" statement as if Lupin was afraid of what Harry 
might have heard and abruptly ends the session, to the scene where 
Lupin enters the shrieking shack with forgiveness in his heart for 
Black with very little explanation. 

Also to be considered, when Harry and the kids' expelliarmus Snape in 
the SS, Black's reply was "You shouldn't have done that
 You should 
have left him to me
" GOF pg. 361 Lupin's reply to that same 
situation was "Thank you Harry"
 
Shouldn't it have been the other way around, Black saying thank you 
and Lupin saying you shouldn't have done that?