The map on the wall behind the sheriff's chair is a slightly altered map of Whidbey Island, Washington, which is about 70 miles south of Vancouver, where the show was filmed.
In the night mass scene, the image of Christ is covered with a black cloth. It is a Catholic tradition to do this before Easter.
This is the only episode of the series not to be named after one specific book of the Bible. (The canon includes four books whose titles begin with "The gospel according to....")