Supernatural: Yellow Fever

The Winchester brothers are investigating a seemingly routine case of healthy men suddenly dropping dead from a sudden heart attack, when Dean becomes infected with 'ghost disease' - a paranormal condition that makes him increasingly frightened by everything, prone to violent scratching and subject to hallucinations.

As well as setting a ticking clock against Dean until his heart gives in, Sam discovers that the disease is targeting people whose personality would class them as "dicks", much to Dean's annoyance.

As his condition gets worse, Jensen Ackles puts in a superb performance as the terrified Dean Winchester, pretty much leaving his brother - and eventually Bobby - to track down the ghost that caused the problem in the first place, and figure out a way to deal with it.

Dean's hallucinations of his greatest fears are particularly telling - Sam transforming into the Yellow-Eyed Demon and Lillith (Sierra McCormick) returning to take him back to Hell - especially in light of the final scene.

Once again, Supernatural delivers another superb episode that continually misdirects, but never cheats, its audience.

Yellow Fever starts out as a darkly humourous, almost slapstick (with the squelchy autopsy) story, then just gets grimmer and grimmer as the narrative progresses and the true horror behind the 'ghost disease' is revealed.

As with Doctor Who's Waters Of Mars the real meat of this episode lies not in the main "in-your-face" plot about the disease and the Winchesters' kicking ghost butt (which was never really in any doubt), but in the character work that writers Andrew Dabb and Daniel Loflin have done with Dean's character - and, by extension, Sam's - in relation to the season's main story arc.

All is not looking good for the Winchesters as they head towards the "Apocalypse", and we're not even a third of the way through the season yet.