An overweight teen becomes excessively thin after eating vegetables tainted with kryptonite, but she also develops a voracious appetite for food---including human flesh. Meanwhile, Clark ponders what to get Lana for her birthday; Whitney gets a tryout for a college football team; and Lex learns some disturbing news about his health.

A corrupt Metropolis police detective sees Clark stop an out-of-control bus barreling toward a homeless man, and the cop threatens to expose the teen's secret unless he does what the lawman wants. Meanwhile, a rich old flame visits Lex and asks him to reconsider his position in his father's company.