“You want to know how it happened, how I became a vampire.”
“Yes,” said the boy. “How did you change, exactly?”
“I can’t tell you exactly,” said the vampire. “I can tell you about it, enclose it with words that will make the value of it to me evident to you. But I can’t tell you exactly, any more than I could tell you exactly what is the experience of sex if you have never had it.”

Interview with The Vampire Part 1