Sheriff Grant Knox is a police officer from upstate New York. He assists the detectives of the Nine-Nine in a Fulton Street Four murder case. Knox appears in The Chopper.
Jake, Charles and Captain Holt travel upstate in search of Mikey D, suspecting he has murdered two members of the Fulton Street Four. Sheriff Knox and his team have Mikey D's residence surrounded and inform the detectives of a barn on the property. While searching the barn, Holt discovers the dead body of Mikey D.