[s4e21] When — The Levee Breaks

: The title is a nod to a 1929 blues song famously covered by Led Zeppelin in 1971.

: Directed by Robert Singer and written by Sera Gamble. It is one of only three episodes in the entire series where no characters die. [S4E21] When the Levee Breaks

" When the Levee Breaks " is the 21st episode of Supernatural 's fourth season and the 69th episode overall. Premiering on May 7, 2009, it serves as the penultimate episode of the season, directly setting the stage for the apocalypse. : The title is a nod to a

: Portrayed as a "villain protagonist" struggling with a supernatural addiction he believes is necessary to kill Lilith and stop the apocalypse. " When the Levee Breaks " is the

: During withdrawal, Sam suffers intense hallucinations, seeing himself tortured by the demon Alastair , being accused of betrayal by his 14-year-old self , and receiving misguided encouragement from a vision of his mother, Mary .

: Ruby reveals that Lilith is "Lucifer's first" demon and that only she can break the final 66th seal.