(season 4 episode 4) Metamorphosis
Sam and Dean learn Jack Montgomery is transforming into Rugaru, a flesh-eating monster. People infected are unaware as to what is going on until they turn into cannibals and begin to eat human beings. Sam tries to reason with Jack so that he will control his urges, but Dean refuses to believe that the urges can be subdued.
Dean is unaware why he was sent back but is enjoying his time with his parents and new-found grandfather, who may be the key to Sam and Dean’s predicament.
