Supernatural is an American paranormal drama television series which follows the paranormal life of Winchester brothers.
Sam Winchester (Jared Padalecki) and
Dean Winchester (Jensen Ackles) travel the country to investigate and battle paranormal events and other unexplained occurrences, many of them based on American urban legends and folklore as well as classic supernatural creatures such as vampires, werewolves, and ghosts.
When Sam was an infant and Dean was a only four years old their mother, Mary, murdered by something supernaturally evil that urged their father, John, to become a fighter of supernatural forces of evil. After the death of Mary the kids was trained by John to hunt and kill all things that go “bump in the night”. At a young age, both Sam and Dean became resourceful sleuths and experienced fighters assisting their father in his quest to destroy dangerous creatures and find the demon that had killed their mother. However, Sam rebelled against the lifestyle his father chose for him, eventually having a falling out with his father and leaving to live a “normal” life. At the age of 22 Sam attended Stanford University on a full scholarship and lived with his girlfriend Jessica (Adrianne Palicki), who was very supportive of him. One night, after years of estrangement, 26 year-old Dean shows up at Sam and Jess to ask for Sam's help to look for their father who had gone missing in three weeks during a “hunting trip”. Sam hesitate to do paranormal hunting again, Dean explained that John has been hunting for more clues to explain the mysterious death of Mary so Sam reluctantly agrees to help Dean in the search.
The brothers trace John to Jericho, California, where they find more clues about their father's possible location and help solve the ghost murder mystery their father had been working on before he disappeared. After all was said and done however and John was yet to be found, Sam declines his brother's invitation to continue the search and conduct more hunts, opting instead to return to his life with Jessica. Unfortunately, when he back in his apartment, he find Jessica dead as the same manner as his mother died. Due to the incident Sam decides to join Dean in the search for their father who may have answers about the demon who killed his mother and his girlfriend. Meanwhile, Sam starts to develop frightening abilities that include death visions, visions of people dying before it actually happens. These visions are somehow connected to the demon who murdered his mother and it's mysterious plans that seem to be all about Sam. Eventually the brothers locate their father, and he reveals the extent of his knowledge of the demon that killed Mary, and his intention to kill it. However, due to a series of catastrophic events (beginning with John's capture), they are eventually overpowered by the demon. While possessing John the demon nearly tortures Dean to death before Sam is able to and shoot it in the leg with the Colt. Sam tries to rush Dean and John to the hospital, but a demon then possesses a semi truck driver and plows into Dean's Impala, demolishing it and leaving all three Winchesters incapacitated inside the wreckage.
In season two, the trio are rescued and taken to the hospital, but Dean is under comatose state. Their father John summons the demon to make a deal and trades the gun and his own life to save Dean. The brothers struggle to cope with John's death while trying to continue their job. Various revelations occurred throughout the season that lead the pair to believe that the special children which have some sort of psychic power that is introduced in the season are being trained to participate in an army that the demon will lead in a coming apocalypse.
In the third season episode “Bedtime Stories”, Sam and Dean argue over whether using the newly rebuilt Colt will help give them the upper hand in breaking Dean's deal with the crossroads demon who revived Sam. At the end of the episode, Sam takes the Colt and, while Dean is asleep, visits the demon and threatens her. She tells Sam, however, that killing her will not break the deal since her boss holds the contract. Sam shoots and kills the demon anyway.