It really does depend on the theme that you want this story to take. I have a couple of ideas to throw into the mix for discussion.
An Odd Meeting (Drama): A naive and impressionable young pizza delivery man is at the door. It is the last delivery, and once when the door opens, he realizes that he has the wrong address. Once he also sees the mess, he profusely offers to help clean the mess that was caused by startling Frederick. Downtrodden, he says that he might as well call it a night and take the heavy cut from his paycheck. It is obvious that this pizza delivery man is weary of his current state of affairs. He has a high tendency to be deceived or used, being overly trusting and loyal. The rest of the story is up in the air.
(optional add-on, religious themes): Having been raised in an authoritarian and sheltered religious household, the man is trying to reconcile with what he experiences from the real world with his colored reinterpretations of reality spoon fed to him as a child, with taboo ridden behavior such as not consuming alcohol and drugs. Though he is tasked to spread the truth of his religion to others, he only proselytizes when he is going door to door as a missionary, and not as a pizza delivery man. The contrast is apparent; the door opens much more often for things which have such limited value as opposed to what should be more important: matters of truth and what gives life meaning.
Bad News (Grimdark, based on White Wolf setting): The one that knows his secret, obviously, is the vampire that sired him. However, a different vampire comes to the door, a messenger that reveals that his sire is dead. This sire was an incredibly notable vampire (think Alucard level epic). Moreover, there have been reports around the rumor mill that acts of heavy ultraviolence have been committed against vampirekind, offsetting the delicate power balance of existing vampire clans in the area that all suspect each other.
It's Turned to Wacky World (Free-For-All Madness/Silliness): There are stranger things that vampires that exist in this world. The main source is believed to be portals to other pocket dimensions. The sky is the limit on what horrors await.
A Combination of All Above: Religious pizza delivery man, sire is dead, ultraviolence against vampires, hellish unimaginable things from unstable portals.
