Maybe a smidge under a 4, but close enough that I couldn't give it a 3 (darn Goodreads for not having half stars)! 
 Laura Griffin really is a master at romantic suspense- I always immediately fall in love with her well-developed characters, her plots are perfectly paced and she really plays to my interests when she describes the world of law enforcement and forensics. 
 Her Tracer series is definitely one to follow, and if I wished she put a little more background information in so I didn't feel like I should be rereading all the previous books to catch up with the current hero and heroine, it is a mere quibble and didn't take much away from my enjoyment of this book.