Ice Cold: Tess Gerritsen

I know I am reading these books out of order, so the introduction of another character threw me for a bit. This book was so different from the others. A back woods adventure packing heat and a lot of surprises and merging stories. A woman goes to a medical conference and meets up with a coworker. They go off with his friends for the weekend and get the car stuck. After finding a mysteriously abandoned community they are hunted to keep from bringing attention to the disappearances and suspicion of foul play.