L i N d $ @ y

I think Lucius did not know (Voldermort would not trust info like that on Lucius). I need a re-read but I think at the end of Book 2, we are led to believe by Dumbledore that Lucius chose to give the diary to Ginny so that the Weasley family image will be tarnished and that Arthur would get into trouble as he's not in good terms with him. The real reason, I need a refresher and I don't know why Lucius will carelessly leave a book in Ginny's cauldron but most certainly it is still an end to carry out whatever Voldemort's plans were and he is to follow that.