The Winchester brothers return to Sioux Falls when the wonderful Sheriff Jody Mills (Kim Rhodes) gives them a call after saving a runaway girl from a vampire attack.
The girl, Alex (Katherine Ramdeen), has spent eight years as a 'blood slave' for a family for vampires and now she's run away, they are on her scent.
The Winchesters go off to track the vamps, while Sheriff Mills takes Alex into "protective custody" in a cabin in the woods (because that locale always works well in horror flicks, right?).
Unfortunately, the brothers discover that Alex has actually working willingly with her vampire family, acting as a lure, drawing victims into secluded ambush sites for the monsters to feed on.
While Sam and Dean get to kick butt and take heads as per normal, Alex Annie Alexis Ann belongs to Sheriff Mills - the brothers really being supporting players in her story - with its themes of loss, grief and motherhood.
The episode only tangentially touches on the season arc, when Sam expresses his concern over Dean's over-enthusiasm in the vampire slaying (a reference to the influence of the Mark of Cain, of course).
In this day and age, vampires have become a rather a tired cliché, but Supernatural always manages to handle them with a deft and original touch.
On top of that, it's always great to see Sheriff Mills, reminding us that there is more to the Winchesters' world than just them and Cas, that their actions affect people's lives in a very real and lasting way.
This is the world-building that helps keep the show fresh and hopefully on our screens for years to come.