ESE!Lupin condensed

[Renee]

No: HPFGUIDX 146803

Renee:

During one of my increasingly rare lurking sessions, I happened upon
the condensed ESE!Lupin post. A very useful summary: I've always had
trouble following the full version. This condensed version is mostly
comprehensible, though still rather convoluted, IMO. 

A few posts back, Neri voiced a number of objections, some of which I
share, but he did not addres the following contention:   
 
Pippin:
 
> Lupin learned of the prophecy. He bargained with Voldemort to 
> save Lily, revealing that Peter was the secret keeper. 

Renee:

I don't get this - probably because I missed the extended version of
this part of the theory. But how did Lupin know Peter was the Secret
Keeper? Who is supposed to have told him? 

Arguably, only four people knew about the Secret Keeper switch to
Peter: Sirius, the Potters and Peter himself. Everyone else, including
DD, believed Sirius was the SK. So, who of these four informed Remus?

Sirius? Certainly not. In the Shrieking Shack, he confirms that he
switched without telling Lupin. (It would have been beyond stupid if
he'd told him, as it's canon he suspected Lupin to be the spy.)

James and Lily? I don't think so. Even if Sirius kept his suspicion  
  of Remus to himself - unlikely as this may be - they would have
guessed from which quarter the wind blew. The spy was "someone close
to the Potters". It wasn't Sirius, or he would not have proposed the
switch in the first place. They didn't think it was Peter, or they
wouldn't have gone along with Sirius's suggestion to switch. So they,
too, must have suspected the only remaining alternative: Lupin. There
is no other option. Lily telling Lupin about the switch because she
does not believe it's him, doesn't work, because the only other
possible spy is Peter. If Lupin is innocent, Peter is not. And unless
Lily's 100% convinced of Peter's innocence, she'll never consent to
making the switch. (And no. Lily being overruled by James is NOT
believable.) 

Which leaves Peter. According to the ESE!Lupin theory, he was not the
spy, but perfectly innocent the moment he was made SK. This would mean
we're dealing with a situation in which a perfectly innocent Peter is
made SK instead of Sirius. *This* Peter knows he's not the spy. He
knows it can't be Sirius either, or Sirius would never have proposed
the switch (see under James and Lily). Ergo, it must be Lupin.
Therefore, Innocent!Peter needs to be extraordinarily daft to tell
Lupin who the real SK is. 

So, is this the situation in the ESE!Lupin theory: Peter tells Lupin
he's the SK, because he is too stupid to add up one and one, and
realise Lupin is the spy? 

Curiously,
Renee