Detective Hank Griffin is a character in the show called Grimm. He is a supportive character in the show that is friends with Detective Nick Burkhardt and Monroe. He is a sidekick almost and best friend of Nick Burkhardt, as well as his partner on police business.
Orginally Hank was unaware of the world of Grimms and Wesen (monsters) and this led him to be the victim of those who were trying to get Nick through him, such as being cursed by a witch. He eventually found out when his best friends daughters was kidnapped, and it turned out she was a peaceful Wesen. Now he knows, Hank assists Nick in his duties to protect the normal people from the secret dangers around them.