Supernatural: Croatoan

When the first English colony, Roanoke, in the New World disappeared mysteriously in the 15th Century the only clue to the settlers' fate was the word "Croatoan" carved on a tree.

When one of Sam's visions leads the Winchester brothers to the small town of Rivergrove, Oregon, he spots the same word carved into a telegraph pole and the boys quickly discover they have walked into the middle of a demonic plague.

The town's folk are rapidly turning violent because of an infection in their blood, which leaves sulphurous traces, that drives them to commit vicious attacks that will allow them to spread the virus through blood contact. This isn't the violent, berserk rage of 28 Days Later, but a more sinister, subtle psychosis.

From a "coming next..." trailer, it had looked as though this episode would be full of gunplay, and while there is probably more shots fired than an average episode of Supernatural, this still isn't the A-Team.

Eventually the Winchesters find themselves holed up in the town's surgery with a handful of other survivors in a set-up reminiscent of Assault On Precinct 13.

Things look hopeless until the brothers get a seemingly lucky break, although only the audience find out what's really going on and the demonic connection that sparked Sam's initial vision. The brothers are left thinking of it as an "unsolved case", but I'm sure this won't be the last we hear of this demonic virus - given the show's writers penchant for keeping major plot threads alive and kicking for as long as possible.

There is a distinct aroma of The X-Files around Croatoan and while the big reveal keeps it firmly within Supernatural territory, there's something oddly scientific about the demons approach that you can't help wondering might have resolved in a more traditionally paranormal way.

The episode ends with another killer cliffhanger as Dean is about to reveal what their father told him in hospital about Sam's abilities...