Supernatural, for those who have so far missed out, follows brothers Dean (Jensen Ackles) and Sam Winchester (Jared Padalecki) as they travel round America in a 1967 Chevy Impala hunting monsters, fighting demons and generally thwarting evil - often in the company of a slightly unhinged angel called Castiel (Misha Collins). At least, they do all that except when they accidentally open the gates of Hell or unleash the apocalypse or whatever; but in fairness, there's generally a totally good reason for such mistakes.
The brothers have variously spent time in heaven, hell and purgatory at this point and endured no end of sibling arguments and gruff, manly reunions, but the chemistry between the cast and the talent in the writing room are such that it all sort of makes sense most of the time. It's also genuinely scary and often very funny; if you think Buffy with lashings more bromance, you wouldn't be a million miles off.
This planned spin-off is to be "planted" in a base location rather than roaming, and will "explore the clashing hunter and monster cultures of Chicago." Given the location the makers - led by Supernatural's supervising producer Andrew Dabb - will have to carefully differentiate it from literature's resident Chicago monster hunter, Jim Butcher's Harry Dresden, and find a cast with the chemistry of the original bunch. Here's hoping they can pull it together.
The first episode of Supernatural s.9 - which we're promised will be a "free-for-all" following the massive upsets of the season 8 finale - just shot in Vancouver, so there's some way to go before we hit this as-yet untitled spin-off episode. Look out for more next year.