Slashy chap, don't like don't read.
Monroe discovered Nick had an unusual kink.
The Grimm became absolutely turned on when the Blutbad woged. Monroe wasn't sure if it was the fur that grew longer, the eyes that grew darker or just the fact that Nick was at his mercy that turned the other one on. All he knew, was that Nick not only struggled to win a Wesen attack when faced with a stronger opponent, the Grimm also had to struggle with his hormones when Monroe was there to protect him.