Snape and GOF

[UNIX4EVR]

No: HPFGUIDX 144346

I'm so confused!

I had finally concluded that Snape was 100% evil.

Then I re-read GOF.

About 100 pages from the end Voldemort gives a little speech to his 
followers.  He says "There are 6 missing.  3 are dead.  1 is a 
coward, and I'll find him.  The other turned against me and I'll 
kill him.  The 6th has returned to me and is at Hogwarts."

He goes on to say the 6th one at Hogwarts helped to get Harry to him 
in the graveyard.  This has to be Barty Crouch, Jr.

The coward has to be Karkaroff.

Which leaves Snape.  "The one who turned against me and I'll kill 
him."

The only other explanation is that Snape was the one who returned to 
him at Hogwarts -- but we get no indication in GOF that Snape had 
anything to do with the tri-wizard cup or killiing BC Sr.

So I'm back to being confused and wondering if Snape ISN'T a good 
guy after all?