Supernatural (TV series)/Recap/S02/E10 Hunted

Season 2, Episode 10:

Hunted
As Sam continues searching for more of the Yellow-Eyed Demon's children, Dean reveals something that John told him before dying: that if he couldn't save Sam, Dean would have to kill him. Working from the Roadhouse, Ash turns up a lead and sends Sam and Dean to a town where a woman named Ava is also having premonitions, including one of a local man's death that later came true. The brothers investigate the dead man's therapy file and learn that he had been communicating with the Yellow-Eyed Demon: apparently, Yellow-Eyes has been creating an army of psychic children to be used as soldiers in an upcoming war.

Meanwhile, Gordon Walker (the vampire hunter) learns this same information from a demon and decides to kill Sam, believing it will help the cause of Hunters. He tracks down the brothers and manages to take Dean prisoner. With help from one of Ava's premonitions, Sam is able to avoid Gordon's trap and save Dean, while the police arrive and arrest Gordon based on an anonymous tip left by Sam. When the brothers check in on Ava, they discover she's missing, her fiancé is dead and there's evidence of demon activity.

Tropes

 * No One Could Survive That: Somehow, Sam survives two grenades going off right next to him.