The episode begins with the return of , a renegade angel who has escaped from Heaven's prison. Convinced that killing Sam Winchester is the only way to prevent him from becoming Lucifer's vessel and starting the Apocalypse, she travels back to 1978 to eliminate John and Mary Winchester before Sam can even be born.
The episode’s climax features the first on-screen appearance of the . To save Mary from Anna and a young Uriel, John Winchester agrees to serve as a temporary vessel for Michael. sobrenatural+temporada+5+ep+13+upd
Michael effortlessly kills Anna and sends Uriel back to Heaven. In a chilling conversation with Dean, Michael reinforces the theme of the season: . He explains that the Winchester bloodline stretches back to Cain and Abel and that no matter what choices they make, the "song remains the same". Trivia and Production Facts The episode begins with the return of ,