How does dean get out of hell in supernatural series 4?

In Supernatural season 4, Dean Winchester is rescued from Hell by Castiel, an angel who is working for God. Castiel uses his angel powers to resurrect Dean and bring him back to life, however because Dean was in Hell for thirty years he brought back a Hellhound with him. Castiel, Dean and the Hellhound return to Bobby's house where Bobby is helping Sam Winchester find a way to kill Lilith, the demon who broke the final seal and released Lucifer from Hell. When Dean was in Hell he was tortured and manipulated by Alastair, a powerful demon who wanted to break Dean's spirit and turn him into a monster. Despite the torturous time in Hell, Dean has returned determined to fight against the forces of evil and help Sam stop Lucifer from destroying the world.