Detective Nick Burckhardt is a Grimm, descended from the Brothers themselves, who it turns out were monster hunters, not folklorists. Only a Grimm can see the monsters' true selves; everyone else sees them as normal people. With the help of a reformed Big Bad Wolf--the only part of the show so far with any signs of life--Nick tracks the bad guy down, and convinces his police partner of the man's guilt via a clue so flimsy (he's humming the same song that was on a previous victim's iPod!) that they ought to thank their lucky stars they're right when they break into the man's house and shoot him to death!
The pilot episode straddles the line between silly and stupid, but most high-concept pilots do. I'm willing to give Grimm another chance next week, but right now, I'm liking ABC's take on real-world fairy tales, Once Upon a Time, a whole lot more.