A homicide detective learns that he is a descendent of a group of hunters known as "Grimms", who fight to keep humanity safe from the supernatural creatures of the world.

Portland homicide Detective Nick Burkhardt (David Giuntoli) discovers he is descended from an elite line of criminal profilers known as "Grimms," charged with keeping balance between humanity and the mythological creatures of the world. As he tries to hide the dangers of his new found calling from his fiancé, Juliette Silverton, (Bitsie Tulloch), and his partner, Hank Griffin (Russell Hornsby), he becomes ever more entrenched in the ancient rivalries and alliances of the Grimm world.

With help from his confidant, Monroe (Silas Weir Mitchell, a reformed Grimm creature himself, Nick must navigate through the forces of a larger-than-life mythology, facing off with Hexenbiests, Blutbads and all manner of ancient evils, including royal lines dating back to the original profilers themselves, The Grimm Brothers.