Lana applied late to Metropolis University, so the only housing near campus she can hope for is the Tri Psi sorority. Turns out, all of the sorority members are vampires, bitten over time and sworn there forever by Buffy Sanders, a meteor freak who was infected when she was bitten by infected vampire bats, who live in caves with stalactites that are filled with kryptonite. As is tradition, only one girl is initiated into Tri Psi per year, and this girl is Lana, who in turn is transformed into a vampire. She gets sharp fangs, sleeps during the day, parties at night, and drinks others' blood. Blah blah blah.
The cooler part of this episode: Lex learns that Milton Fine is ruining his image in Fine's college class, and discovers that Fine is researching Lex's ethically questionable projects for a book. Lex knows that Fine has Clark as his special assistant for this research. Lex threatens Fine's professor job, while Fine threatens to reveal Lex's projects publicly.
By the end of the episode, the audience has to be asking themselves two questions: "What in the world was the vampire thing all about?" and "Is Fine good or evil? What are his motives?" And are his motives ever so insidious, it's worse than Lex could ever think of doing at this point in his increasingly dark life.