Ideas For Book/Novel!

Okay, I have the Characters setup. And, A partial introduction. But, What I really need is a PLOT! I mean, Its going to be a Vampire/Human love story. But- A GOTHIC Vampire/Human love story. I mean... The Human is a bit troubled and Misunderstood. And, The Vampire is.. Well... Im not sure! Thats why; I, Myself, Need a background for The Vampire. I have a little jotted down...
Like, For instance...By, The way.. His name is Art.
But, Like... I want to put him in a Mysterious, Dark, Passionate way. Could You Help?