This is the fourth book in the series.

Ed Davies is a Linker, a special kind of investigator that doesn’t work for any official agency and specializes in serial crimes. He has a new partner, Karen, and they work out of an RV in south Florida.
Lucena Burning is a serial killer and is currently living on a boat and enjoying the party culture of various islands in the Bahamas. She has reunited with her long time accomplice, Ron, and eventually gets an itchy trigger finger.
Over time, Ed has become obsessed with finding Lucena. Their paths come close, but never quite cross until…
Come along for an adventure that spans Florida and ventures off into the Bahamas and New Orleans. Along the way there will be near death experiences, pirates, romance, strippers and fresh roasted fish food.

You can buy Parallel here