Supernatural - Season 2, Episode 10, Hunted
Sam is shocked when Dean finally tells him their dad asked him to watch over Sam to save him, or if that fails kill him. Sam leaves alone to let Ash look up a same-type clairvoyant demonic victim. Ava Wilson, from Peoria, Indiana, fits that bill and looks up Sam to warn she saw his death, then leaves ridiculing him. Dean followed Sam, just in time to intervene when crazy Gordon Walker turns up, who will stop at nothing to destroy 'utterly evil' Sam. It's a testing fight for the brothers.