Highly respected judge Logan Patterson is murdered, and shortly after several other people who played some part in the conviction and incarceration of an escaped giant of unnatural strength. Nick is badly wounded, out of action. Monroe however shows unusual enthusiasm to help out while Hank follows the paper trail.

Nick is puzzled by several cases where a suspect who escaped the police is violently dealt with by a masked, cloaked avenger. He even leaves Nick messages, suggesting he is a 'real Grimm' who is cleaning up 'weakling' Nick's messes. But he strikes terror even with gentle Wesen, like the beavers, who seek help through Monroe, who fears it's a descendant of a medieval Grimm vigilante order. Nick suspects a police mole.

Ranchhand John is killed while accidentally bumping at night into Vincent, a blue-fluorescent feral performing one of the 27 raids on cows that went from Nebraska to Portland, actually harvesting bovine ovaries for his pregnant mate Jocelyn, with whom he keeps moving and hiding. Besides Nick, the case seems to be followed only by an 'ufologist' or alien-hunter, who in fact chases the very feral species. Monroe recognizes the print Nick made from his key as part of a medieval map as Swabia, Renard explains the keys combine into a map to a terrible treasure hidden by seven crusader Grimms. Juliette swears Monroe to secrecy, being insecure about her reemerging love memories.