|Airdate||December 7th, 2006|
|Written by||John Shiban|
|Directed by||Robert Singer|
|Previous episode||Crossroad Blues|
|Episode list||Season 2|
In a small Oregon town, there is some kind of supernatural disease that one person can pass on to another by blood to blood contact.
Sam has a vision of Dean killing a man tied to a chair, leading them to River Grove, Oregon, where Sam recalls the story of the Roanoke Colony when he stumbles across the word "CROATOAN" carved into a street side telephone-power pole.
Sam and Dean seek out the man in Sam's vision, and discover increasingly violent people, who appear to be controlled by some kind of "demonic virus". They discover that all lines of communication - radio, phone, cell signal - has been cut off from the town, and when he attempts to leave via road, Dean discovers a roadblock, made up of 'infected' locals who fire upon him.
Dean and Sam hole up in the local medical center, with the local doctor, a nurse and 'Sarge' (an ex-marine). The doctor studies the blood of an infected person, noting that there appears to be traces of sulfur in the blood, leading Sam to further suspect demonic intervention. The demon virus is transmitted via exchanging blood, but the sulfur does not manifest in the blood until four hours after infection. Sam speculates that it could be related to a theory in John's Journal, that Croatoan is the name of a demon associated with plague and pestilence, and calls what's going on "demonic germ warfare".
Duane Tanner, the man Sam saw in his vision and whose family Sam and Dean first encountered exhibiting signs of infection, turns up at the medical center, claiming to have been out of the town fishing and just returned.The medical center occupants suspect he might be infected, and they restrain him by tying him to a chair.
Recognizing the scene from his vision, Sam tries to convince Dean not to kill Duane, as they don't know yet whether he's infected with the demon virus or not. Dean locks Sam in a room to stop him from preventing the killing, but Dean is unable to follow through anyway.
Sam and Dean use medical supplies to build explosives, building an arsenal to help them escape the town, as the infected townspeople are milling about outside. The nurse of the medical center attacks Sam, deliberately cutting her hand and his chest to exchange blood and ostensibly infecting him with the demon virus. Dean kills the nurse. Believing Sam to be infected, the remaining people in the medical center decide to leave in the Impala. Dean elects to stay with Sam, and seems to be on the cusp of sharing some innermost thought when the doctor returns with the news that the rest of the townsfolk have disappeared.
Five hours later, the doctor announces that there is no trace of the demon virus in Sam's blood either, therefore he wasn't infected. This leaves both Sam and Dean uneasy. The team in the medical center go their separate ways, Duane riding in Sarge's truck.
Duane asks Sarge to pull over because he "has to make a call", and draws out a goblet and knife. Slitting Sarge's throat, Duane catches the blood in the goblet. When he swirls, it starts whirlpooling, and Duane speaks into it as if he's communicating with someone (though we only hear one side of it), saying, "I don't think any more tests will be necessary... The Winchester boy, definitely immune as expected." Duane's eyes then turn black, indicating that he's probably possessed the entire scene, reminiscent of Meg in 1.11 Scarecrow.
Sam and Dean end up on the shore of a river, drinking beer and talking. Dean is on the cusp of revealing the big secret John told him in 2.01 In My Time of Dying when the episode ends.
- The Croatoan Virus would not be mentioned again until the Season 5 episode The End.
- This episode is the third to involve Sam's immunity the first being Nightmare, the second Simon Said, in this episode it introduces the fact that not only is Sam immune to demonic powers to an extent but to a demonic virus as well.
- Azazel seemed to have released this virus as a test possibly to test Sam's body as a reference to what's to come in Season 5.
- Sam: This is the dumbest thing you've ever done.
Dean: I don't know about that. Remember that waitress in Tampa?
- Finnish: Vaarallinen virus (The Dangerous Virus)
- French: Croatoan
- German: Croatoan
- Polish: Croatoan