Who is Scorcher Kennedy from Faithful Place: A Novel and what is their importance?

Known as "Scorcher," Mick Kennedy is a detective in the murder division. Scorcher and Frank have a rivalry that causes some animosity. Scorcher becomes the lead detective when Rosie's body is discovered and is also involved in the investigation into Kevin's murder. He is very proud of the percentage of cases he solves and obviously feels superior to the officers in Frank's division.