Sam and Dean are called in to investigate a mysterious airplane crash, and soon realize that a demon was responsible. It intends to eliminate the survivors of the crash, and is willing to kill hundreds to achieve its goal.

Sam and Dean hear about a man who died of a stroke while in front of a mirror. After visiting the family and interviewing the man's two daughters, the brothers conclude that the legendary Bloody Mary caused the man's death.

One of Sam's friends, Zach, is accused of murder, and Sam offers to help him by checking up on his younger sister, Rebecca. While visiting her, Rebecca convinces the brothers that Zach didn't commit the murder because he was with him when the murder happened. But could Zach be in two places at the same time?

The brothers come across a girl whose boyfriend fell victim of the Hook Man. It's up to Sam and Dean to destroy the ghost's bones before she and her father become victims as well.

A gas & power worker is killed when insects burrow themselves into his brain and consume it. Sam and Dean research the history of the new housing development and find that it has been constructed on former Indian land cursed against the white man. Now, it's up to the brothers to get the people out before they are killed by swarms of bees, locusts, spiders, and beetles.

Sam continues to have haunting dreams and convinces Dean to return home for the first time. There, the brothers have to deal with painful memories, but their feelings are put on hold when the current residents experience the same phenomena that Sam had dreamed about. But before they can stop what's happening now, Sam and Dean have to face their mother's death first.

Sam and Dean travel to an abandoned sanitarium where they find that the patients once revolted against cruel and unusual punishments given to them by the head doctor. The brothers search the area for lost college students, but the spirits make them go insane, and end up turning Sam against Dean.

Sam and Dean part ways when Sam insists on ignoring John's orders and tracking down Jessica's killer. Dean travels to a town that's hiding a dark secret about a scarecrow, and their perpetual prosperity, while Sam meets up with an attractive hitchhiker.

During a fight with a hobgoblin, Dean is electrocuted, causing deadly damage to his heart. Sam tries to find a way to save Dean, and comes across a preacher who claims he can cure the incurable. But the brothers soon discover that the preacher's miracles are happening due to help from the Grim Reaper, who trades one life for another, "less worthy" life.

Dean and Sam travel to Missouri after Cassie, one of Dean's ex-girlfriends, calls him to investigate two racially motivated murders. They find that each murder involves a black truck that has no driver and leaves no tracks. Meanwhile, Dean has to deal with the feelings that he still has for Cassie.

Sam has a premonition about a man's death that is staged to look like a suicide. Once Sam convinces Dean to investigate the case, they are puzzled when they can't find proof that something supernatural was behind the death. However, they soon realize that the dead man's son, Max, has telekinesis and is using it to kill off his abusive family members.

Sam and Dean head to Minnesota where a young boy witnesses a man vanish into thin air. Shortly after arriving, Sam is targeted by the same abductor, and Dean is left to search for his brother. However, the brothers discover that their kidnappers are humans, using the captives as human prey for their sadistic "hunting expeditions."

While following a lead concerning a mysterious death in Chicago, Sam reunites with Meg. Sam suspects it's more than a coincidence, and Meg soon ambushes Sam and Dean. She explains that it's a trap... for John, using them as bait.

Dean and Sam track down the ghost of Mordechai Murdoch, who haunts an old Texas farmhouse. However, the brothers discover that Mordechai is a tulpa, created by thousands of people believing in it after the fake legend of him was posted on a popular website. Now, Sam and Dean must stop the spirit from killing any more people who enter the house.

When Sam and Dean find articles about a town where children are inexplicably falling into comas, the brothers discover that a Shtriga, a creature that attacks children, is behind the mysterious comas. During the battle, Dean remembers a past battle with the creature that almost resulted in Sam's death.

When a young couple mysteriously die after buying a portrait of a 1910 family, Sam and Dean travel to the scene to investigate the painting. The brothers find that each owner of the painting has ended up dead due to a dangerous spirit bound to the portrait. Can they stop it before it kills again?

When a vampire hunter and friend of their father's is killed, Sam and Dean are shocked when their father arrives to help them solve the crime. John finds that vampires have stolen a gun that has the capability of killing all evil beings. The brothers, along with their father, set out to get the gun back.

After Sam has a vision of a family being attacked by a demon, similar to the way his mother was attacked, the Winchesters follow demonic signs to Salvation, Iowa, to kill the demon using the Colt. However, Meg calls the family to let them know if they don't give her the gun, she is going to kill their friends.

To save their father, Sam and Dean enlist the help of a family friend, Bobby Singer. When Meg shows up at Bobby's home, the brothers are able to exorcise the demon from her body and get her to tell them where their father is being held. The brothers race off to rescue their father, resulting in a final showdown between the Winchesters and the demon they have spent their lives looking for.