Supernatural (TV series)/Recap/S04/E02 Are You There God? It's Me, Dean Winchester

Season 4, Episode 2:

Are You There God, It's Me Dean Winchester
Sam, Dean, and Bobby are haunted by the spirits of people they failed to save. This is the "Rising of the Witnesses", one of the 66 seals broken before Lucifer is released and the apocalypse comes.

Tropes

 * Creepy Twins: The little girls who haunt Bobby.