Season One consists of 22 episodes that aired in the United States beginning September 13, 2005, and ending May 4, 2006. The first sixteen episodes aired on Tuesdays at 7:00 pm, after which the series was rescheduled to Thursdays.
In 1983, the Winchesters John, Mary and their two sons Dean and Sam were a normal family living in Lawrence, Kansas but one night a powerful yellow-eyed demon named Azazel killed Mary for an unknown reason. Over the next 22 years John raised his boys as hunters, human vigilantes who hunt down supernatural creatures and beings, while John looked for the demon who killed Mary and the means to kill it. Dean was always protective of his brother and loyal to his father, but Sam was always resistant to both of them and the hunting life itself, and he eventually left to attend Stanford on a full ride.
In 2005, Sam has retired from hunting to focus on college, but Dean brings him back into that life after their father John goes missing and after Sam comes back from hunting a ghost with Dean, Sam's girlfriend Jessica Moore is killed by Azazel, just like their mother was. The two brothers then embark on hunting quests across the country as they look for John and also work on cases involving other supernatural creatures, from ghosts, to shapeshifters, deities, even vampires and other monsters. Along the way, they discover that Sam has unusual abilities such as telekinesis and visions of the future, which the boys come to think is related to the demon they're hunting. Sam and Dean also face the recurring villain Meg, a demon minion of Azazel.
Eventually the boys find their father, who has discovered the means to kill Azazel: an old, antique revolver called The Colt, a supernatural firearm weapon created in 1835 by Samuel Colt to kill anything supernatural--but it only has a limited amount of bullets. After finding The Colt, John is forced by Meg to hand it over. He instead uses a fake gun while Sam and Dean attempt to kill Azazel with the real one, but the demon escapes and John is captured. Sam and Dean, with the help of old and close family friend Bobby Singer, find and exorcise Meg from her host, get John's location and find him, but only have two Colt bullets left. Azazel is revealed to be possessing John and announces that he has plans for Sam; he tries to kill Dean, though John re-takes control while Sam shoots him in the leg, forcing Azazel to leave John's body.
As the three Winchesters leave with their war-wounds to re-track Azazel, a demon in a truck rams into the Impala, smashing it and knocking out the family.
- Jeffrey Dean Morgan as John Winchester (8/22) and Azazel (3/22)
- Nicki Aycox as Meg (4/22) and Meg Masters (1/22)
- Samantha Smith as Mary Winchester (2/22)
- Adrianne Palicki as Jessica Moore (2/22)
- Sebastian Spence as Tom (2/22)
- Jim Beaver as Bobby Singer (1/22)
Episode List: 2005-2006
|Along a lonely California highway, a mysterious woman in white lures men to their deaths - a terrifying phenomenon that may be the brothers' first clue to their father's whereabouts.|
|Deep in the Colorado woods, deep in horror. Sam and Dean's search for their father, and for the evil power that killed Jessica, leads to the blood-soaked path of a Wendigo, a cannibal spirit of Native American lore.|
|Dead In The Water||9/27/05||3||1.03|
|Is a series of drownings in a Wisconsin lake the work of a vengeful spirit? A young eyewitness, traumatized into silence by the shock he experienced, may have the power to prophecy the next drowning.|
|A plane reservation is a ticket to terror when a demon forces a jet into a crash landing. Knowing demon is on another flight, Sam and Dean board to attempt an in-air exorcism.|
|An incantation uttered during a game of truth or dare unleashes a ghost who "lives" in mirrors...and kills by gouging out the eyes of her prey.|
|A demonic shape-shifter adopts the likeness of Sam's college buddy to commit a gruesome murder. When the brothers investigate, the being "borrows" Dean's form to continue the killing spree.|
|In a quiet Iowa college town, a minister prays to protect his parishioners' children. But another minister - a two-centuries-old madman with a hook for a hand - wants them terrified, slashed and dead.|
|After a construction worker is killed by insects burrowing into his brain, the brothers investigate a town's history and find that a new housing development is being built on sacred Indian land - with a curse attached.|
|After 22 years, A new family moves into the brothers' old home, Sam and Dean return to their childhood home and, if Sam's nightmares are correct, this house has yet another evil hidden inside.|
|The brothers investigate a long-shuttered mental asylum that has the power to drive intruders mad...and murderous.|
|A malevolent scarecrow could be why strangers to Burkitsville, Indiana don't get out of town alive.|
|Faith healer Roy Le Grange cures Dean after an accident leaves him near death. But for every life Le Grange saves, another life must end.|
|The devil's down in Dixie - and he's driving one scary truck. Sam and Dean investigate when something wheeled, metallic and evil forces a series of African-American drivers off the road to their deaths.|
|The brothers pose as priests to gather information at a house visited by a sudden death- a death Sam saw in a dream. But precognition may be just the start of the preternatural powers Sam suddenly possesses.|
|A nice decoration for the wall. A backwards family of hunters likes to stuff and mount kill as trophies. Only they hunt humans. And they've got Sam.|
|Dean and Sam are investigating a mysterious murder in Chicago and discover that Meg is responsible for it. However, when they try to catch her, Meg unleashes shadow spirits on them.|
|Sam and Dean investigate the case of a maniacal ghost inhabiting a long abandoned Texas farmhouse known as "Hell House." They believe the ghost is the spirit of a deceased Depression-era farmer who killed his family.|
|John sends Sam and Dean on a hunt for creature that eluded John before. Once there, Sam and Dean discover children across town are falling ill. What could be attacking the children and what connection does it have to the boys' past?|
|A portrait of a long-dead family has the spirits of the father and daughter trapped inside and someone is murdering its owners.|
|Dead Man's Blood||04/20/06||20||1.20|
|After an aging spook hunter falls prey to the vampires he thought he had long ago destroyed, John Winchester joins his sons to battle the bloodsuckers - and retrieve an unearthly gun they possess.|
|Meg's back. And she wants the Colt. So she starts killing John's old friends one by one until he agrees to hand over the weapon - even if it means leaving his sons alone to battle the demon that killed their mother.|
|Sam and Dean, in order to save their father from Meg, enlist the help of a family friend, Bobby. When Meg shows up at Bobby's, the brothers are able to exorcise the demon from her body and get her to tell them where their father is being held. Sam and Dean race off to rescue their father, resulting in their first showdown between the Winchesters and the Yellow-Eyed Demon they have spent their lives looking for.|
- Main Antagonist: Azazel
- Secondary Antagonist: Meg
- The first season is the only season so far to not use Carry On Wayward Son in its finale. Instead, the song was used in the penultimate episode, with Fight the Good Fight used in the finale. It plays during the opening of Episode 21 (Salvation).