Marauders and Voldemort

[potioncat]

No: HPFGUIDX 110201

DuffyPoo:
snip
If Snape really knew who stole them, he wouldn't be saying this to 
HP, as HP never took any of it.  He's trying to make HP angry enough 
to confess or spill the beans. He later threatens HP with 
Veritaserum, "And then, Potter .. then we'll find out whether you've 
been in my office or not,."   (because I don't know yet, but I 
suspect it was you, and I'd really like to have proof of this so DD 
would have to expell you!)   Harry doesn't like the sound of this 
because he knows him spilling the truth would land "a whole lot of 
people in trouble -- Hermione and Dobby, for a start --"  
> 

Potioncat:
I hope it isn't too late to rejoin this thread.

But, at the point that Snape is trying to find out "If you've been 
in my office" he isn't thinking of the episode in CoS.  He's 
wondering who is stealing the ingredients now in GoF. (Crouch!Moody) 
although both Harry and the reader thinks Snape is referring to the 
CoS incident.

I've argued that both polyjuice potion and the map may indeed be 
Dark Magic.  I'm less sure of the map, if only because it's come up 
again in the book without any character questioning it.