Why Suspect Sirius?

[dicentra63]

No: HPFGUIDX 40136

--- In HPforGrownups at y..., "ssk7882" <skelkins at a...> wrote:
> Sarah wrote:
> 
> > One reason I would suspect Lupin as being somewhat-evil...  During 
> > the Conversation in the shrieking shack, between Lupin and Sirius, 
> > Lupin, says that he was not told about the switch to Peter as the 
> > secret keeper, because Sirius suspected Lupin as being in alliance 
> > with Voldemort. 
> 
> > That doesn't really make sense. Why would Sirius and James suspect 
> > Lupin over Peter? 
> 
> Well, primarily, I think that they suspected him because he is a 
> werewolf.

<snip a definitive explanation of why that belongs in the Lupin FAQ>

OK, then.  That takes care of why James and Sirius suspected Lupin.
Now, why did Lupin suspect Sirius?  Hmm?  Everyone knew James and Siri
were like brothers and that James trusted Siri.  Or is Lupin's casual
"forgive me for believing *you* were the spy" apply only to Sirius's
time in Azkaban?  The suspicions that there was a spy amongst them
predate the Potters' murders.  Wouldn't Lupin have had *his*
suspicions?  Wouldn't he have to wonder if Sirius was the one?  If
not, was he suspecting Peter and didn't say anything?  Or did he
*know* it was Peter and didn't sound the alarm? Oh HO! LYCANTRHOPE
raises its vulpine head!

--Dicentra, who reads that passage as applying to both pre- and post-
Pottermurder