What were the Malfoys DOING there?

[potioncat]

No: HPFGUIDX 113142

Magda: 
> And it's interesting that he didn't just give the diary to Snape 
and
> get him to plant it someplace where a kid could "accidently" find 
it.

Potioncat:
Oh, good question!  For the all the ideas out there that Snape has 
dinner at the Malfoys each week, they don't seem to be working 
together do they?  Or has Harry just not seen it?

Well, let's see.

Lucius is acting on his own agenda and doesn't want Snape in on it?

Lucius doesn't know that Snape was a DE and doesn't yet trust him? 
info?

I was always puzzled by the explanation that Malfoy was trying to 
discredit Arthur.  And that could be the reason.  But was DD 
misleading Malfoy?  DD let Malfoy know that DD knew who gave the 
diary to Giny.  But does DD know it was for a different reason?

Can you tell I don't do mysteries or spy stories very often?
Potioncat