Due South

The movie that the TV series was spun off from.  When a legendary Canadian Mountie is murdered, his son (and fellow RCMP) Constable Benton Fraser follows the trail of his killers to Chicago, where he teams up with a local cop to bring them to justice. However, he soon finds that the trail leads closer to home than he ever imagined.
He's kind. He's polite. He's a cop?