A homicide detective begins having weird hallucinations in which he sees people as monsters. One is a blonde woman, another is a suspect in the police station. All becomes clear when he's visited by his cancer-dying aunt, who explains that their family is descended from a long line of monster hunters. He's getting the power to see them because she's dying. Basically, all the stories from Grimm's Fairy Tales are real. And because of this the monsters call them Grimms. The main villain here is a creature, sort of like a werewolf, that goes after young girls dressed in red, as in LITTLE RED RIDING HOOD. The detective gets the help of a reformed monster, who helps track this supernatural serial killer to his cabin in the woods. There are some attempts at humor, which fall flat. And the main character is no BUFFY or ANGEL, as that's what the show is obviously being compared to.
This is one of the most underwhelming television pilots of the 2011 season, up there with ONCE UPON A TIME in terms of lackluster. Stick with one of the best monster-hunter series of all time, SUPERNATURAL.