Nick is descended from a line of creature hunters known as Grimms, who have the responsibility to protect the rest of mankind from the creatures who are known as Wesen. Aunt Marie also tells him that the trailer she brought contains information and equipment to help him in his task. gives Nick a small antique key and tells him to protect it with his life as "they" want it. With help from Monroe, a Blutbad he met while working on case, and Rosalee Calvert, a Fuchsbau, Nick deals with crimes involving several different types of Wesen ranging from the bear-like Jägerbars to the rat-like Reinigen.