Chamber of Secrets - plot to make terrible things happen at Hogwarts

[dracojadon at yahoo.co.uk]

No: HPFGUIDX 171806

Apologies if this has been discussed before (Yahoo's search server  
has been funny all day).

At the beginning of CoS, Dobby warns Harry: "If Harry Potter goes  
back to Hogwarts, he will be in mortal danger [...] There is a plot  
[...] to make most terrible things happen at Hogwarts [...]. Dobby  
has known it for months."

How does Dobby know -- how does Lucius know -- what Riddle will  
choose to do, or if Ginny/some other student will try writing in the  
diary at all?

Is opening the Chamber of Secrets the plot referred to?

Jadon