Annie Porter (Bullock) is thrilled when her boyfriend Alex Shaw (Patric) surprises her with two tickets for a cruise to the Bahamas aboard the Seabourn Legend. The trip is a peace offering presented because Annie has just learned that Alex is a police officer who has been lying about his choice of profession. What the couple do not realize is that the disgruntled John Geiger (Dafoe), the person who created the software that operates the ship's computer systems, has plotted a violent takeover of the vessel and a diamond hijacking that puts everyone on board in mortal danger.