Big Black Hole by Wilma Kahn

PI Gayle Fisher needs to leave town fast. While she debates how to accomplish that, a new client walks in and gives her the perfect route. The case seems a little iffy, but the client insists that his sister didn’t really kill herself, and he’s willing to put his money on it. Gayle tucks the cash in her wallet, hops in her 10-year-old silver LeMans and heads out of town, but once she reaches the sleepy tourist village on the shores of beautiful Lake Michigan, things turn ugly.