Kirk's Landing by Mike Young

Dave Browne, an undercover cop, is busted when his cloaking power fails in the middle of a biker gang meeting. Forced to hide out as detachment commander in Kirk's Landing, a small Manitoba town, his only goal is to continue as a loner and lay low for a year. He learns that it's hard to stay a loner in a small town, though, especially with everyone eager to meet him and enlist his help with their version of the local issues. Dave finds his detective instincts pulling him into an unsolved disappearance, corruption in the local high tech paper mill, and pollution of the local lakes and rivers.
When Dave tries to use his invisibility to help him in his investigations he discovers there are darker forces at work-forces that are now targeting him, changing him. It's now up to his friends to decide if he can be saved in time.