The series begins with a series of investigations by investigator Charlie Hudson in front of a group of criminals inside the city. Charley, a leading crime investigator at St John's Police Department, is trying to co-operate with an unusual partner - Rex (Diesel von Burgimwald) to beat these criminals. Rex is a former German pastor K9, who keeps her senses high for her recruitment with Charlie to find criminals for the investigation of perplexing crimes.