How does Petunia know about Dementors?

[Eustace_Scrubb]

No: HPFGUIDX 97009

amlesis wrote:
> 
> Hi, I am new to the list and English is not my first language so I
apologise for spelling and grammar mistakes. I also hope the topic
below was not the subject of previous discussions.

Now, Eustace_Scrubb:
Welcome to HP4GU!  Almost all of us have recycled topics, so don't
worry too much about that...

Amlesis again
<snips> 
> Another detail I found interesting, Petunia and Vernon are not very
impressed when hearing LV's name but Petunia is really scared of
Dementors. 
> Amlesis

I agree that Vernon doesn't react much to LV's name...until he sees
what an effect it has on Petunia.  But I would say Petunia is _very
impressed_ by what Harry has told them:

" 'Back?' whispered Aunt Petunia.
   She was looking at Harry as she had never looked at him before.
And all of a sudden, for the very first time in his life, Harry fully
appreciated that Aunt Petunia was his mother's sister...Her large,
pale eyes...were wide and fearful. The furious pretence that Aunt
Petunia had maintained all Harry's life - that there was no magic and
no world other than the world she inhabited with Uncle Vernon - seemed
to have fallen away.
    'Yes,' Harry said, talking directly to Aunt Petunia now.  'He came
back a month ago. I saw him.'
    Her hands found Dudley's massive leather-clad shoulders and
clutched them." (OOTP, Chapter 2, A Peck of Owls)

What Petunia seems to fear the most about the Dementors is that they
may have been sent by LV.  What does Petunia know about LV and why he
killed Lily?  For unless she has reason to think that she and Dudley
are now in danger from him, I wouldn't expect such a strong
reaction...yes, as you say, Lily was Petunia's sister, but why would
Petunia fear that LV might come after her?  And what exactly was the
arrangement with Dumbledore?...I don't think we've heard that fully
either.

I think we'll get this question answered "canonically"...in the
meantime it's fun to speculate.

Cheers,

Eustace_Scrubb