When five friends accidentally cause a fatal car accident, they cover up their involvement and make a pact to keep the accident a secret so they don't have to bear the consequences. A year later, their past catches up with them and they have to face a terrible truth: someone knows what they did last summer... and plots revenge. As the friends are chased by a killer one by one, they discover that this has happened before, and turn to two survivors of the legendary 1997 Southport Massacre for help.