Season 3 begins with the brothers Winchester hunting down the demons that were released from the gates of hell. They realize that hunting down the hundreds of spirits that escaped from the Devil’s Gate—a doorway to Hell briefly opened at the end of the previous season—will be an enormous task. With only a year left to live—he made a demonic pact to resurrect Sam—Dean decides to live life to the fullest and exhibits a carefree attitude that troubles Sam, who is trying to find a loophole. Bobby calls their attention to the manifestation of the 7 deadly sins. During the scuffle, a mysterious blonde named Ruby (Katie Cassidy) saves Sam and kills three demons with a magical knife—demons are typically immune to physical harm—before departing. The rest of the Sins are exorcised. As Sam continues his research the next day, Dean reveals that a clause in his pact will end Sam’s life if he tries to escape the deal.
Dean reconnects with an old love who has a young son and initially thinks her son could be his. It turns out to be not but the brothers do help them against changelings. Ruby reveals herself as a demon to Sam. Sam is soon the target of fellow hunters Kubrick & Walker who believe that Sam must die due to his inhuman nature. Bella Talbot in introduced as a procurer and seller to the highest bidder and steals a cursed lucky rabbit’s foot from the brothers. Dean tricks her into becoming cursed, forcing her to allow the foots destruction. Kubrick later visits Gordon in prison again. Believing the coincidences that helped him to locate Sam were caused by God, he agrees to help Gordon break out of prison. Casey, a demon, reveals to Dean that her world is in disarray following the demon Azazel’s death and Sam’s failure to replace him as leader. The brothers & Bella have to join forces to battle a ghost ship, the viewing of which makes a ghost kill the viewer.
Gordon is tuned into a vampire and kills Kubrick and is later killed by Sam. Next the brothers tackle a killer Santa Claus. After helping the brothers stop a trio of powerful witches, controlled by a single on, Ruby admits to Dean that she cannot save Dean and asks his help to prepare Sam for life without him. Bela steals the Colt from the brothers while they help Bobby battle his dreams. The Trickster plagues the brothers making Sam relive Dean’s death over and over again, until they face him face to face. The brothers are caught by Henriksen and his men, tipped off by Bella, and have a showdown with a bunch of demons at a local prison. Henriksen finally is convinced that the Brothers are innocent but after the Winchesters leave, Lillith in the form on a small girl comes and kills them. Sam & Dean next meet up with the Ghostfacers – Harry & Ed and their crew who are shooting the pilot of their new reality show. They then have to face a monster that makes people listen to the voices of dead loved ones/people who’s death troubled them and thus victims are committing suicide.
Rufus, a semi-retired hunter is also introduced to the series as he helps Dean. Bella is presumably killed when her 10 years is up – she had made a deal with a crossroads demon for fortunes and a life of riches away from her abusive father. With only 30 hours left until Dean’s contract ends, Bobby tracks Lilith to New Harmony, Indiana. Dean does not want to attack unprepared, but refuses to seek help from Ruby due to her ambiguous nature. Sam nevertheless secretly summons her and requests her demon-killing knife. In their fight against Lillith, Ruby’s human body is killed and her demon spirit is sent away. Lilith telekinetically pins the brothers down as her hellhound mauls Dean to death. Lilith then blasts Sam with white energy from her hand. Horrified to see that it has no effect, she flees her host before Sam can retaliate. A devastated Sam cradles Dean, whose soul is then shown in Hell hanging from a vast landscape of chains and meathooks.