In the hospital after the car crash, while one Winchester considers making the ultimate sacrifice to save the others, another must deal with a stalking Reaper.
Still reeling from their father's death, the Winchester brothers go after a demonic clown that can only be seen by children and whose goal is to eat their parents.
A series of beheadings and cow mutilations draw the brothers to Montana where they discover a gang of vampires. But these vampires don't want to be mindless hunters. So when Gordon, the other demon hunter, attempts to take down the entire gang, he puts all of their lives in jeopardy, as they battle each other.
The Brothers help a college kid who has resurrected his college crush. But instead of falling in love with him as he'd hoped, the resurrected girl has gone to murdering her ex-boyfriend and the woman he cheated with.
The Winchester Brothers encounter a hippie named Andy, whose family was visited by the Demon that killed their own mother. The boys come to suspect Andy of using psychic powers to commit murder, but a dark secret from Andy's family might actually be the cause and solution to these murders.
Blonde women go missing and the Winchester Brothers suspect the soul of a serial killer is responsible. But their investigation takes a turn for the worst when the ghost captures Jo.
The Winchester Bros. are in hot water after an investigator pins a pair of murders on them. But when she begins to receive visions, the boys are able to convince her of the existence of ghosts, and together they learn that the ghost isn't killing people, but trying to alert future victims of the ghost's own murderer.
The Winchester Brothers attempt to deal a fatal blow to a deal-making demon, but when it offers Dean the chance to see his father all bets are off.
Sam dreams that Dean shoots a man. Reality begins to mirror the dream when the brothers travel to Crater Lake, Oregon, where a blood-borne demon virus is wreaking havoc. When one of the townspeople transfers the virus to Sam, Dean is forced to consider killing his own brother. But, ominously, Sam demonstrates an immunity to the disease. Soon after, the townspeople vanish into thin air and Sam and Dean are left with their own demons.
Dean reveals to Sam the big secret his father told him: the demon who killed their mother has special plans for Sam that he intends to execute if Dean doesn't keep him on the right path.
The Winchester Brothers look into some suspicious deaths at a century-old hotel where the proprietor's daughter might be the key to finding the killer... via her imaginary friend. But the demon is, in fact, trying to use the little girl to take over her body.
The Winchester Brothers look into a mysterious string of bank robberies wherein a top employee robs the bank then commits suicide. With the help of a night watchman from one of the robbed banks, they ascertain that the shape-shifter has returned.
People claiming to have been visited by angels commit terrible murders in the name of God, and Sam and Dean investigate their assertions. But while Dean doubts even the existence of God, Sam is convinced these people are telling the truth.
Dean gets a phone call from Sam, who's been missing for 10 days and doesn't know where he is or how he got there. Once they meet up, the Winchester Brothers discover that Sam has killed a man in cold blood. But Dean finds out that it wasn't Sam who killed, but the demon inside him. Sam, possessed by the demon, goes to Minnesota to kill Jo and Bobby, but Dean arrives in time and together, he and Bobby banish the demon back to Hell.
Despite getting on each other's last nerve, the Winchester Brothers try to solve the murder of an ethics professor in a college town. But the potentially ghostly manner of his death conjures up even more ghoulish circumstances in the boys' detective work, so they decide to call in for some help from their fellow hunter Bobby.
Sam and Dean try to help a woman who's just survived a car wreck but is now being chased by a demented farmer, whom the Winchester Brothers discover is actually an evil spirit bent on killing this woman to fulfill its yearly ritual.
The Winchester Brothers go to San Francisco to look into a murder that looks to be the work of a werewolf. Sam quickly takes to the victim's attractive secretary, and the two strike up a physical relationship.
Sam and Dean try to stop a ghost that is wreaking havoc on a Hollywood movie set.
The Winchester Brothers get themselves thrown in jail on purpose in order to take out a ghost that's killing inmates. But when dogged FBI agent Henricksen arrives at the prison, they realize that killing the ghost and busting out of prison is not going to be that simple.
Dean hunts something called a Djinn -- basically, a genie -- and winds up being transported to a parallel universe where Sam is in law school, engaged to his deceased ex-girlfriend, and their mother is alive.
The Yellow-Eyed Demon captures Sam and puts him with other kids who have special abilities with the intent of forming an army to destroy the human race.
Sam dies, but Dean manages to bring him back to life by selling his own soul. That reaper will come looking for his soul in one year's time. In the meantime, the Winchester Brothers try to stop Jake from opening a portal to hell that will allow The Demon who killed their mother to wage war on Earth.