The hunt for Azazel, the Yellow-Eyed Demon

Two brothers, Sam and Dean Winchester, witness their mother's paranormal death as children and grow up trained to fight by a distraught father who wants nothing more then to hunt down the thing that killed his wife. Sam escapes to college to start a new, normal life, but gets pulled back in after Dean shows up on his doorstep to tell him their father is missing. Following clues from an eerie phone message from him, the boys travel to a small town and encounter a vengeful spirit called the "Woman in White" who then starts to haunt Sam.

In suburban Nebraska, a group of partying high school teens jokingly dare their friend Charlie to look into the mirror and repeat "Bloody Mary, Bloody Mary, Bloody Mary," not knowing this will unleash a series of mysterious murders. Sam and Dean realize that Bloody Mary has the power to travel through all reflective surfaces when she is hunting a victim. Worried that teens are accidentally summoning Bloody Mary, Sam and Dean race to destroy the violent spirit before she can kill again.

While battling a demon, Dean is electrocuted, resulting in permanent damage to his heart and leaving him with only a couple of months to live. A despondent Sam searches desperately for a way to save his brother and believes he may have found an answer through a preacher who claims to heal the incurable. However, Dean and Sam discover that the preacher is getting help from the Grim Reaper who is trading one life for another he feels is less worthy.

Sam has a premonition in which a man is killed, but the murder is made to look like a suicide. Sam convinces Dean that they must investigate the case, but the two are puzzled when they fail to find anything that indicates that the death was supernatural in nature. That is, until they find out that Max, the reclusive son of the first victim, has been using his recently acquired power of telekinesis to kill the family members that once abused him. Sam also discovers Max's mother was killed by the same fiery demon that took his own mom.

After Daniel Elkins, a vampire hunter and John's mentor, is murdered, Sam and Dean are surprised when John himself shows up to solve the case. John discovers the vampires have taken an antique gun, which has the power to kill all supernatural beings. The Winchester family sets out to retrieve the gun from the vampires so they can use it to kill the demon that took Sam and Dean's mother.

Sam has a vision of a family being attacked in the same manner as the attack on his mom, so he, Dean and John head off to Salvation, Iowa, to save this family and finally kill the demon using the Colt gun. However, Meg calls and lets the family know she is going to start killing their friends unless they return the gun. John meets Meg to deliver a fake gun, while the boys are left to deal with the demon.

On a mission to save their father from Meg, Sam and Dean seek help from an old family friend, Bobby. When Meg shows up on Bobby's doorstep, the brothers lure her into a trap and exorcise the demon from her body after learning where John is being held prisoner. While trying to rescue John, the demon shows up and a full battle ensues between the Winchesters and the demon they have been searching for all their lives.

Sam, Dean and John were left for dead after the Demon plowed a semi into the Impala. Now, one of the Winchesters hovers between life and death as the surviving family must face an old and powerful adversary.

Sam and Dean listen to a message on John's cell phone from a woman named Ellen and decide to track her down. They are shocked to discover Ellen runs a road house that also serves as a gathering place for hunters like themselves. Meanwhile, at a small town carnival, a clown is persuading children to let them into their home so he can murder their parents.

Sam and Dean meet Andy, a slacker who has psychic powers of persuasion, which he uses to gain favors from people. However, when some of Andy's friends start dying, the brothers question whether Andy is using his powers to kill. After learning that Andy's family was visited by the Demon 22 years ago, Sam wonders if Andy is part of the group of children the Demon told him about, and if that means he himself will eventually turn evil.

When two highly successful professionals die after claiming to be haunted by hellhounds, Sam and Dean investigate the local dive bar and discover it sits upon a site where a deal-making demon has been making people's dreams come true in exchange for their souls. Dean summons the demon to exorcise it but is horrified after it reveals the painful truth about John's death and tempts Dean by offering him the one thing he wants more than anything - his father.

After Sam has a vision of Dean killing a young man who seems to be possessed by a demon, the two brothers head off to Oregon to search for answers. They come across a town infected by a deadly virus that drives a person to kill. Sam becomes infected by one of the locals and prepares for his deadly fate, but after nothing happens to him, Dean decides to come clean and reveal what John whispered to him before he died.

After Dean tells Sam what their father told him before he died, a distraught Sam sneaks off to Indiana without Dean. While there, Sam runs into Ava, a psychic who confesses to Sam she sought him out to warn him of his impending death. Dean discovers Gordon is after Sam and races to find his brother in time to save him.

After receiving a frantic call from Sam, who has been missing for over a week, Dean races to his brother's side. He finds Sam covered in blood, but unable to remember anything that happened. Upon investigation, the brothers are horrified to discover a tape that shows Sam killing another hunter in cold blood, causing Sam to believe his evil side is finally taking over.

Sam and Dean call upon their family friend and fellow hunter Bobby for help after they are stumped by violent and unexplainable happenings on a local college campus. Bobby arrives with a suspicion as to the culprit behind the killing spree and the brothers' escalating feud.

Sam is abducted by the Yellow-Eyed Demon and finds himself in a ghost town with other children who have special abilities. They learn the Demon has brought them together to initiate his endgame: an all-out war against the human race. In an effort to encourage Sam to fight, the Demon shows him what really happened to one of his parents. Dean enlists Bobby's help to find Sam before the battle begins, but he arrives too late.

Dean must deal with the aftermath of the fight between Sam and Jake and pays a steep price for his involvement. The Demon and his spirits threaten to overtake the hunters until they receive help from an unexpected ally.