Use of the Time-Turner to Help Sirius in PoA

[Rita Winston]

No: HPFGUIDX 11673

--- In HPforGrownups at y..., katgurl2k at y... wrote:
> Could someone maybe help me with this?  Harry and Hermione use the 
> Time-Turner to go back three hours to help Sirius and Buckbeak 
> escape.  (snip)  Wouldn't it have made more sense to go back (snip)
> and make sure that Lupin took his potion?

"No!" said Hermione in a terrified whisper. "Don't you understand?
We're breaking one of the most important wizarding laws! Nobody's
supposed to change time, nobody! You heard Dumbledore, if we're 
seen --"


"Exactly! You wouldn't understand, you might even attack yourself! 
Don't you see? Professor McGonagall told me what awful things have 
happened when wizards have meddled with time.... Loads of them ended
up killing their past or future selves by mistake!"