This show is a lot like Buffy the Vampire Slayer and the like, but with less darkness and more slap-stick comedy. Which is surprisingly a good mix.
The show starts off very funny. I LOL several times in the first 10 minutes.
At the half-way point they eased you into the darkness. Hey, it's about having your soul sold to the devil, gotta have some element of darkness. ;) There were some parts where it was darn right serious, but always followed up with a bit of humor to help you shake it off.
So here we have Sam...his parents sold his soul to the devil, and now 21 years later the devil has come to collect. Sam is charged to help the devil in retrieving evil people that belong in Hell. For how long, well the devil won't say.