S04E09: 'I Know What You Did Last Summer'

Ruby warns the Winchesters that a young woman who can hear what angels are thinking is being hunted by a powerful demon called Alastair.

But rather than helping unravel why Castiel brought Dean back from Hell, Anna drops a bombshell about when her gift began and what the angels really think of the brothers.

Soon, Ruby's interest in Anna and her power over Sam begins to arouse Dean's suspicions and he demands to know exactly why his younger brother has such faith in her.

His reluctance to trust Ruby leads Sam to recount how he spent the six months after Dean's death, including how he learned to control his powers and the true nature of his relationship with Ruby.

Elsewhere, Dean's own faith in Castiel is tested when he returns with Uriel and reveals his plans for Anna.