S04E04: 'Metamorphosis'

Dean discovers Sam's secret and comes face-to-face with Ruby for the first time since returning from Hell.

Sam insists that what he is doing with Ruby is actually for the greater good until Dean drops the bombshell that God himself has requested that he stop. Dean warns Sam that he is on a "slippery slope".

The boys' moral dilemma ties in nicely with this week's investigation. Fellow hunter Travis tips them off about a Rougarou called Jack - a seemingly normal human who is slowly metamorphosising into a monster with an insatiable appetite for raw meat.

According to Travis, Jack can satisfy his hunger by devouring human flesh, thereby becoming a monster forever, adding that the only known way to kill a Rougarou is by fire.

Of course, the Winchesters have opposite ideas about this. Sam thinks that Jack can learn to control his urges while Dean is more in favour of killing him. Ultimately, the boys' need to put their differences aside to try to save Jack in a dramatic and very gruesome climax.