Four couples set out on a self-drive three-day river cruise. Brett and Crystal, both in relationships with other partners, discover a deep attraction for each other. This does not go unnoticed, and anger and resentment begin to simmer between the friends. On the last day of the trip, the group is shocked to find Crystal missing. A thorough search fails to find her. She has disappeared without a trace. Three years pass and a body is found. Under the direction of attractive Detective-Sergeant Stephanie Darrieux, the group reunites. During her investigation, Darrieux uncovers some disturbing secrets. Not everyone is as they appear to be, and four people will meet horrendous deaths before the mystery is solved.