When Special Agent Raleigh Harmon boards a cruise ship to Alaska, the Last Frontier seems like a dream destination for a forensic geologist. She also wants to leave behind a hectic work schedule and a marriage engagement drained of romance.

But as soon as a passenger is found dead, Raleigh’s vacation gets lost at sea. The ship’s security chief wants to rule the death a suicide, but Raleigh’s experience in forensics offers a much darker conclusion: Somewhere onboard this ship, a ruthless murderer walks free.

Engulfed by one of her toughest cases yet, Raleigh requests assistance from the FBI. Only it comes from her nemesis—handsome Special Agent Jack Stephanson. As the cruise ship sails through Alaska’s Inside Passage, Raleigh has five days to solve a high-profile murder, provide consultation for a movie filming onboard, and figure out her increasingly complicated feelings for Jack—who might not be as arrogant as she thought.

Like the scenery that surrounds the cruise ship, Raleigh discovers a mystery so daunting that even the mountains might bow down before it.