Where Dean is a Federal Marshal and he stumbles across this town hidden in the middle of the mountains while on a roadtrip with his brother to take him to Stanford.
They get stranded when Baby gets wrecked in a crash and start exploring the quirky little mountain town. Dean makes friends with a little girl, Claire Novak, autistic and quiet, but who talks to him shyly and sweetly and spouts off random math equations.
This leads to him meeting her father, Castiel, the town librarian, who seems to also be extremely well versed in Quantum Physics and military procedures.
Dean and Sam get caught up in disappearing people and strange flashing lights and discover everyone in town are completely intelligent and working as government scientists.
Dean realizes that the only one who knows how to fix the equation is Claire and is the only one who believes she can do it, and she does, because the new guy is nice and cute and doesn't treat her differently.
And when the old sheriff, Bobby Singer, gets paralyzed in the resulting blast, Dean is brought on to take his place while Sam decides to stick around to try and learn more about the anti-gravity machine the mechanic is working on (it has nothing to do with his cute assistant, Jessica, shut up).
Maybe Dean spends a lot of time at the library between cases, so what?